ConstraintLayout 使用

相对位置属性(layout_constraint[自身控件位置]_[目标控件位置]="[目标控件ID]")、Margin属性、goneMargin属性、Bias属性(在对齐父容器后，设置水平与竖直的比例)、Ratio属性(layout_constraintDimensionRatio设置View的高宽比)、Chains链状结构(layout_constraintHorizontal_chainStyle、layout_constraintVertical_chainStyle...)、Guideline

RecyclerView 使用

可通过设置LayoutManager来快速实现ListView、GridView、瀑布流的效果，横向纵向显示、ItemAnimation

RecyclerView 多Item布局实现

  @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        return super.onCreateViewHolder(parent, viewType);
    }
    @Override
    public int getItemViewType(int position) {
        return super.getItemViewType(position);
    }

    @Override
    public int getViewTypeCount() {
        return super.getViewTypeCount();
    }

列表界面的封装(分页、上拉加载)

// fragment基类
public abstract class BaseFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View rootView = inflater.inflate(returnFragmentLayout(), container, false);
        ButterKnife.bind(this, rootView);
        return rootView;
    }

    public abstract
    @LayoutRes
    int returnFragmentLayout();

    public abstract void viewCreated();

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        viewCreated();// 此处调用初始化View方法
    }
}

// 列表Adapter基类
public abstract class BasePageListAdapter<T> extends RecyclerView.Adapter {
    /**
     * item类型
     */
    public static final int ITEM = 1;
    public static final int FOOTER = 2;

    @IntDef({NULL, LOADING, LOADMORE, COMPLETE, CUSTOM})
    @Retention(RetentionPolicy.SOURCE)
    public @interface LoadState {
    }
    ...
    public BasePageListAdapter(Context context, @LayoutRes int itemResourceId, List<T> data) {
        this.context = context;
        this.itemResourceId = itemResourceId;
        
        setItemResourceId();
    }
    /**
     * if use the constructor with param of the resource iD of item layout, you can ignore this method,
     * else the resource AGENCY_ID of item layout should be assigned to itemResourceId ;
     *
     * @see #itemResourceId
     */
    public abstract void setItemResourceId();
    ...
    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, final int position) {
        if (position == getItemCount() - 1 && loadingState != NULL) {
            // footer 样式
            ...
            if (customFooterView != null && customFooterView.getVisibility() == View.VISIBLE) {
                // 下一页有数据了
                customFooterView.setVisibility(View.GONE);
            }
            switch (loadingState) {
                case LOADING:
                    tip.setVisibility(View.VISIBLE);
                    tip.setText("拼命加载中...");
                    progressBar.setVisibility(View.VISIBLE);
                    break;
                case LOADMORE:
                    ...
                    break;
                case COMPLETE:
                    ...
                    break;
                case CUSTOM:
                    if (customFooterView != null) {
                    // 数据已加载完并为自定义Footer
                        customFooterView.setVisibility(View.VISIBLE);
                        tip.setVisibility(View.GONE);
                        progressBar.setVisibility(View.GONE);
                        if (footerViewHolder.itemView.findViewWithTag("footer") == null) {
                            ...
                            ((LinearLayout) footerViewHolder.itemView).addView(customFooterView);
                        }
                    }
                    break;
            }
        } else if (position < data.size()) {
            distributeData(viewHolder, data.get(position));
        }
    }

    public abstract void distributeData(ItemViewHolder viewHolder, T data);

    /**
     * this BaseRecycleAdapter include two type of view-- normal item and footer;
     *
     * @param position get item type with the position
     * @return type
     */
    @Override
    public int getItemViewType(int position) {
        if (position == getItemCount() - 1 && loadingState != NULL) return FOOTER;
        else return ITEM;
    }
    @Override
    public int getItemCount() {
        int footer = loadingState != NULL ? 1 : 0;
        return data.size() + footer;
    }
    // 自定义 Footer
    public void setCustomFooter(View customFooterView) {
        this.customFooterView = customFooterView;
        this.customFooterView.setTag("footer");
        setLoadingState(CUSTOM);
        notifyDataSetChanged();
    }

    /**
     * check if RecyclerView is ready to callback the method-- onLoadNext,
     * you should call this method before you want to callback
     * {@link com.tech2real.listener.RecyclerLoadNextListener.OnLoadNextListener}
     *
     * @param ready is the RecycleView ready to call method onLoadNext()
     */
    public void setReadyToLoadNext(boolean ready) {
        this.ready = ready;
    }

    public boolean isReadyToLoadNext() {
        return ready;
    }
...
}

// 列表页抽象类
public abstract class BaseListFragment<T> extends BaseFragment implements BasePageListAdapter.OnItemClickListener<T>,
        SwipeRefreshLayout.OnRefreshListener, RecyclerLoadNextListener.OnLoadNextListener {
    ...
    @BindView(R.id.recycler)
    public RecyclerView mRecycler;

    protected BasePageListAdapter<T> adapter;

    @IntDef({NULL, SEARCH, ERROR, NORMAL, CUSTOM, LOADING, COMPLETE})
    @Retention(RetentionPolicy.SOURCE)
    public @interface interfaceType {
    }

    public int page = 1;
    public int number = 10;

    @Override
    public int returnFragmentLayout() {
        return R.layout.common_page_list;
    }

    @Override
    public void onRefresh() {
        loadFirst();
    }

    public void loadFirst() {
        page = 1;
        setUIState(LOADING);
        loadData();
    }

    @Override
    public void onLoadNext() {
        if (number > 0) {
            page++;
            loadData();
        }
    }

    public abstract void loadData();

    protected void handleData(List<T> data) {
        if (data == null || data.size() == 0) {
            if (page == 1) {
                setUIState(NULL);
                adapter.clear();
            } else {
                setUIState(COMPLETE);
            }
        } else {
            setUIState(NORMAL);
            if (number < 0 || data.size() < number) {
                adapter.setLoadingState(BasePageListAdapter.COMPLETE);
            } else {
                adapter.setLoadingState(BasePageListAdapter.LOADMORE);
            }

            if (page == 1) {
                adapter.replaceItems(data);
            } else {
                adapter.addItems(data);
            }
        }
    }

    public void setUIState(@interfaceType int resultState) {
        switch (resultState) {
            case NULL:
                adapter.setLoadingState(BasePageListAdapter.NULL);
                break;
            case ERROR:
                adapter.setLoadingState(BasePageListAdapter.NULL);
                break;
            case NORMAL:
                break;
            case LOADING:
                adapter.setLoadingState(BasePageListAdapter.LOADING);
                break;
            case COMPLETE:
            default:
                adapter.setLoadingState(BasePageListAdapter.COMPLETE);
                break;

        }
        setRefreshing(false);
    }
...
}

public class RecyclerLoadNextListener extends RecyclerView.OnScrollListener {
    ...
    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        try {
            BasePageListAdapter adapter = (BasePageListAdapter) recyclerView.getAdapter();

            LinearLayoutManager layoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();

            int last = layoutManager.findLastVisibleItemPosition();
            int total = layoutManager.getItemCount();

            if (total - 2 <= last && mNextListener != null && adapter.isReadyToLoadNext()) {
                // 加载下一页
                adapter.setReadyToLoadNext(false);
                mNextListener.onLoadNext();
            }

        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}

自定义CircleImageView，源码解析

public class CircleImageView extends ImageView {

    private static final ScaleType SCALE_TYPE = ScaleType.CENTER_CROP;

    private static final Bitmap.Config BITMAP_CONFIG = Bitmap.Config.ARGB_8888;
    private static final int COLORDRAWABLE_DIMENSION = 2;

    private static final int DEFAULT_BORDER_WIDTH = 0;
    private static final int DEFAULT_BORDER_COLOR = Color.BLACK;
    private static final int DEFAULT_FILL_COLOR = Color.TRANSPARENT;
    private static final boolean DEFAULT_BORDER_OVERLAY = false;

    private final RectF mDrawableRect = new RectF();
    private final RectF mBorderRect = new RectF();

    private final Matrix mShaderMatrix = new Matrix();
    private final Paint mBitmapPaint = new Paint();
    private final Paint mBorderPaint = new Paint();
    private final Paint mFillPaint = new Paint();

    private int mBorderColor = DEFAULT_BORDER_COLOR;
    private int mBorderWidth = DEFAULT_BORDER_WIDTH;
    private int mFillColor = DEFAULT_FILL_COLOR;

    private Bitmap mBitmap;
    private BitmapShader mBitmapShader;
    private int mBitmapWidth;
    private int mBitmapHeight;

    private float mDrawableRadius;
    private float mBorderRadius;

    private ColorFilter mColorFilter;

    private boolean mReady;
    private boolean mSetupPending;
    private boolean mBorderOverlay;
    private boolean mDisableCircularTransformation;

    public CircleImageView(Context context) {
        super(context);

        init();
    }

    public CircleImageView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public CircleImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CircleImageView, defStyle, 0);

        // 自定义属性
        mBorderWidth = a.getDimensionPixelSize(R.styleable.CircleImageView_civ_border_width, DEFAULT_BORDER_WIDTH);
        mBorderColor = a.getColor(R.styleable.CircleImageView_civ_border_color, DEFAULT_BORDER_COLOR);
        mBorderOverlay = a.getBoolean(R.styleable.CircleImageView_civ_border_overlay, DEFAULT_BORDER_OVERLAY);
        mFillColor = a.getColor(R.styleable.CircleImageView_civ_fill_color, DEFAULT_FILL_COLOR);

        a.recycle();

        init();
    }

    private void init() {
        // 默认为 ScaleType.CENTER_CROP 且不可修改
        super.setScaleType(SCALE_TYPE);
        mReady = true;

        if (mSetupPending) {
            setup();
            mSetupPending = false;
        }
    }

    @Override
    public ScaleType getScaleType() {
        return SCALE_TYPE;
    }

    @Override
    public void setScaleType(ScaleType scaleType) {
        // 为什么限定?
        if (scaleType != SCALE_TYPE) {
            throw new IllegalArgumentException(String.format("ScaleType %s not supported.", scaleType));
        }
    }

    @Override
    public void setAdjustViewBounds(boolean adjustViewBounds) {
        // 为什么限定?
        if (adjustViewBounds) {
            throw new IllegalArgumentException("adjustViewBounds not supported.");
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if (mDisableCircularTransformation) {
            super.onDraw(canvas);
            return;
        }

        if (mBitmap == null) {
            return;
        }

        if (mFillColor != Color.TRANSPARENT) {
            canvas.drawCircle(mDrawableRect.centerX(), mDrawableRect.centerY(), mDrawableRadius, mFillPaint);
        }
        canvas.drawCircle(mDrawableRect.centerX(), mDrawableRect.centerY(), mDrawableRadius, mBitmapPaint);
        if (mBorderWidth > 0) {
            canvas.drawCircle(mBorderRect.centerX(), mBorderRect.centerY(), mBorderRadius, mBorderPaint);
        }
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        setup();
    }

    @Override
    public void setPadding(int left, int top, int right, int bottom) {
        super.setPadding(left, top, right, bottom);
        setup();
    }

    @Override
    public void setPaddingRelative(int start, int top, int end, int bottom) {
        super.setPaddingRelative(start, top, end, bottom);
        setup();
    }

    public int getBorderColor() {
        return mBorderColor;
    }

    public void setBorderColor(@ColorInt int borderColor) {
        if (borderColor == mBorderColor) {
            return;
        }

        mBorderColor = borderColor;
        mBorderPaint.setColor(mBorderColor);
        invalidate();
    }

    /**
     * @deprecated Use {@link #setBorderColor(int)} instead
     */
    @Deprecated
    public void setBorderColorResource(@ColorRes int borderColorRes) {
        setBorderColor(getContext().getResources().getColor(borderColorRes));
    }

    /**
     * Return the color drawn behind the circle-shaped drawable.
     *
     * @return The color drawn behind the drawable
     *
     * @deprecated Fill color support is going to be removed in the future
     */
    @Deprecated
    public int getFillColor() {
        return mFillColor;
    }

    /**
     * Set a color to be drawn behind the circle-shaped drawable. Note that
     * this has no effect if the drawable is opaque or no drawable is set.
     *
     * @param fillColor The color to be drawn behind the drawable
     *
     * @deprecated Fill color support is going to be removed in the future
     */
    @Deprecated
    public void setFillColor(@ColorInt int fillColor) {
        if (fillColor == mFillColor) {
            return;
        }

        mFillColor = fillColor;
        mFillPaint.setColor(fillColor);
        invalidate();
    }

    /**
     * Set a color to be drawn behind the circle-shaped drawable. Note that
     * this has no effect if the drawable is opaque or no drawable is set.
     *
     * @param fillColorRes The color resource to be resolved to a color and
     *                     drawn behind the drawable
     *
     * @deprecated Fill color support is going to be removed in the future
     */
    @Deprecated
    public void setFillColorResource(@ColorRes int fillColorRes) {
        setFillColor(getContext().getResources().getColor(fillColorRes));
    }

    public int getBorderWidth() {
        return mBorderWidth;
    }

    public void setBorderWidth(int borderWidth) {
        if (borderWidth == mBorderWidth) {
            return;
        }

        mBorderWidth = borderWidth;
        setup();
    }

    public boolean isBorderOverlay() {
        return mBorderOverlay;
    }

    public void setBorderOverlay(boolean borderOverlay) {
        if (borderOverlay == mBorderOverlay) {
            return;
        }

        mBorderOverlay = borderOverlay;
        setup();
    }

    public boolean isDisableCircularTransformation() {
        return mDisableCircularTransformation;
    }

    public void setDisableCircularTransformation(boolean disableCircularTransformation) {
        if (mDisableCircularTransformation == disableCircularTransformation) {
            return;
        }

        mDisableCircularTransformation = disableCircularTransformation;
        initializeBitmap();
    }

    @Override
    public void setImageBitmap(Bitmap bm) {
        super.setImageBitmap(bm);
        initializeBitmap();
    }

    @Override
    public void setImageDrawable(Drawable drawable) {
        super.setImageDrawable(drawable);
        initializeBitmap();
    }

    @Override
    public void setImageResource(@DrawableRes int resId) {
        super.setImageResource(resId);
        initializeBitmap();
    }

    @Override
    public void setImageURI(Uri uri) {
        super.setImageURI(uri);
        initializeBitmap();
    }

    @Override
    public void setColorFilter(ColorFilter cf) {
        if (cf == mColorFilter) {
            return;
        }

        mColorFilter = cf;
        applyColorFilter();
        invalidate();
    }

    @Override
    public ColorFilter getColorFilter() {
        return mColorFilter;
    }

    private void applyColorFilter() {
        if (mBitmapPaint != null) {
            mBitmapPaint.setColorFilter(mColorFilter);
        }
    }

    private Bitmap getBitmapFromDrawable(Drawable drawable) {
        if (drawable == null) {
            return null;
        }

        if (drawable instanceof BitmapDrawable) {
            return ((BitmapDrawable) drawable).getBitmap();
        }

        try {
            Bitmap bitmap;

            if (drawable instanceof ColorDrawable) {
                bitmap = Bitmap.createBitmap(COLORDRAWABLE_DIMENSION, COLORDRAWABLE_DIMENSION, BITMAP_CONFIG);
            } else {
                bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), BITMAP_CONFIG);
            }

            Canvas canvas = new Canvas(bitmap);
            drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
            drawable.draw(canvas);
            return bitmap;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    private void initializeBitmap() {
        if (mDisableCircularTransformation) {
            mBitmap = null;
        } else {
            mBitmap = getBitmapFromDrawable(getDrawable());
        }
        setup();
    }

    private void setup() {
        if (!mReady) {
            mSetupPending = true;
            return;
        }

        if (getWidth() == 0 && getHeight() == 0) {
            return;
        }

        if (mBitmap == null) {
            invalidate();
            return;
        }

        // Shader used to draw a bitmap as a texture. The bitmap can be repeated or mirrored by setting the tiling mode.
        // BitmapShader的作用是使用特定的图片来作为纹理来使用
        // CLMP   如果需要填充的内容大小超过了bitmap size 就选bitmap 边界的颜色进行扩展
        // REPEA  T重复，不断的重复bitmap去填满，如果绘制的区域大于纹理图片的话，纹理图片会在这片区域不断重复
        // MIRROR 镜像的去填满。如果绘制的区域大于纹理图片的话，纹理图片会以镜像的形式重复出现
        mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);

        mBitmapPaint.setAntiAlias(true);
        mBitmapPaint.setShader(mBitmapShader);

        mBorderPaint.setStyle(Paint.Style.STROKE);
        mBorderPaint.setAntiAlias(true);
        mBorderPaint.setColor(mBorderColor);
        mBorderPaint.setStrokeWidth(mBorderWidth);

        mFillPaint.setStyle(Paint.Style.FILL);
        mFillPaint.setAntiAlias(true);
        mFillPaint.setColor(mFillColor);

        mBitmapHeight = mBitmap.getHeight();
        mBitmapWidth = mBitmap.getWidth();

        mBorderRect.set(calculateBounds());
        // 为什么是这样算的?
        mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2.0f, (mBorderRect.width() - mBorderWidth) / 2.0f);

        mDrawableRect.set(mBorderRect);
        if (!mBorderOverlay && mBorderWidth > 0) {
            // inset 将一个Drawable嵌入
            mDrawableRect.inset(mBorderWidth - 1.0f, mBorderWidth - 1.0f);
        }
        mDrawableRadius = Math.min(mDrawableRect.height() / 2.0f, mDrawableRect.width() / 2.0f);

        applyColorFilter();
        updateShaderMatrix();
        invalidate();
    }

    // 计算Border绘制区域
    private RectF calculateBounds() {
        int availableWidth  = getWidth() - getPaddingLeft() - getPaddingRight();
        int availableHeight = getHeight() - getPaddingTop() - getPaddingBottom();

        int sideLength = Math.min(availableWidth, availableHeight);

        float left = getPaddingLeft() + (availableWidth - sideLength) / 2f;
        float top = getPaddingTop() + (availableHeight - sideLength) / 2f;

        return new RectF(left, top, left + sideLength, top + sideLength);
    }

    // 控制变换
    /**
    Matrix是Android提供的一个矩阵工具类，本身不能对图像或组件进行变换，但它可以和其它API结合起来控制图形、组件的变换； 
    Matrix提供了如下方法来控制平移、旋转和缩放： 

    setTranslate(float dx,float dy)：控制Matrix进行平移； 
    setSkew(float kx,float ky,float px,float py)：控制Matrix以px,py为轴心进行倾斜，kx,ky为X,Y方向上的倾斜距离； 
    setRotate(float degress)：控制Matrix进行旋转，degress控制旋转的角度； 
    setRorate(float degress,float px,float py)：设置以px,py为轴心进行旋转，degress控制旋转角度； 
    setScale(float sx,float sy)：设置Matrix进行缩放，sx,sy控制X,Y方向上的缩放比例； 
    setScale(float sx,float sy,float px,float py)：设置Matrix以px,py为轴心进行缩放，sx,sy控制X,Y方向上的缩放比例； 


    Andorid的API提供了set、post和pre三种操作：
     
    set是直接设置Matrix的值，每次set一次，整个Matrix的数组都会变掉； 
    post是后乘，当前的矩阵乘以参数给出的矩阵。可以连续多次使用post，来完成所需的整个变换。 
    pre是前乘，参数给出的矩阵乘以当前的矩阵。所以操作是在当前矩阵的最前面发生的。
    */
    private void updateShaderMatrix() {
        float scale;
        float dx = 0;
        float dy = 0;

        mShaderMatrix.set(null);

        if (mBitmapWidth * mDrawableRect.height() > mDrawableRect.width() * mBitmapHeight) {
            scale = mDrawableRect.height() / (float) mBitmapHeight;
            dx = (mDrawableRect.width() - mBitmapWidth * scale) * 0.5f;
        } else {
            scale = mDrawableRect.width() / (float) mBitmapWidth;
            dy = (mDrawableRect.height() - mBitmapHeight * scale) * 0.5f;
        }

        mShaderMatrix.setScale(scale, scale);
        mShaderMatrix.postTranslate((int) (dx + 0.5f) + mDrawableRect.left, (int) (dy + 0.5f) + mDrawableRect.top);

        mBitmapShader.setLocalMatrix(mShaderMatrix);
    }

}

图片加载框架

Picasso使用

// 简单使用
Picasso.with(this).load(url).into(imageView);
// 同步
  try {
           Bitmap bitmap =  Picasso.with(this).load(URL).get();
        } catch (IOException e) {
            e.printStackTrace();
        }
// 异步
Picasso.with(this).load(URL).fetch(new Callback() {
          @Override
          public void onSuccess() {
              //加载成功
          }
          @Override
          public void onError() {
            //加载失败
          }
      });

Target target = new Target() {
            @Override
            public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
                if (progressBar != null) progressBar.setVisibility(View.GONE);
                if (imageView.getTag() == this) {
                    imageView.setImageBitmap(bitmap);
                    Palette.Builder bulider = Palette.from(bitmap);
                    Palette palette = bulider.generate();
                    dominantColor[0] = palette.getDominantColor(Color.WHITE);
                }
            }

            @Override
            public void onBitmapFailed(Drawable errorDrawable) {
                if (progressBar != null) progressBar.setVisibility(View.GONE);
            }

            @Override
            public void onPrepareLoad(Drawable placeHolderDrawable) {
            }
        };
        imageView.setTag(target);
// 缓存策略
.memoryPolicy(MemoryPolicy.NO_CACHE,MemoryPolicy.NO_STORE)