看了上一篇，对view的绘制过程有了一定了解了。 下面动手做一个。
学习自定义ViewGroup 实现tagView
网上有很多flowlayout，可参考他们的实现。这里的目的是学习view的绘制过程。部分参考网上代码
//简单的tagview实现就是，多个tag,计算每个tag的长宽，计算当前行能显示几个，不够长了就换下一行显示。
顺序：measure()-onMeasure()-layout()-onLayout()-draw()-onDraw();
这个顺序面试有见过考这个的。
一般自定义都是重写onXxxx开头的，不带的不可以重写
例：viewGoup:
@Override
public final void layout(int l, int t, int r, int b) {}
@Override
protected abstract void onLayout(boolean changed,
int l, int t, int r, int b);
重写onMeasure
重要地方都有注释~
需要for循环所有子类，计算子类的高度。-----此处默认高度都是一致的
private int mTotalLength;
private final int margin = 5;
void measureVertical(int widthMeasureSpec, int heightMeasureSpec) {
mTotalLength = 0;
//此处计算的是当前view的大小
int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);
int modeWidth = MeasureSpec.getMode(widthMeasureSpec);
int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);
int modeHeight = MeasureSpec.getMode(heightMeasureSpec);
int count = getChildCount();
//计算每个子类的大小
int maxCalcWidth = 0;//最大宽度，当前view的width为wrap_content时有效
int singleWidth = 0;//当前行宽度
int realMaxWidth = sizeWidth - getPaddingLeft() - getPaddingRight();//去除当前view的padding就是子类可使用的大小
mTotalLength += getPaddingTop() + getPaddingBottom();
for (int i = 0; i < count; i++) {
InnerTv child = (InnerTv) getChildAt(i);//InnerTv继承textView啥都没做,可以不用重写子view的onMeasure。。
if (child == null) {
continue;
}
measureChild(child, widthMeasureSpec, heightMeasureSpec);//计算子view的宽高
int childWidth = child.getMeasuredWidth();
int childHeight = child.getMeasuredHeight();
if (i == 0) {
//首高
mTotalLength += childHeight;// 所有item高度一致，不换行
}
if (singleWidth + childWidth + margin > realMaxWidth) {//超出最大宽度
//下一行
maxCalcWidth = Math.max(maxCalcWidth, singleWidth);
singleWidth = childWidth;
mTotalLength += childHeight + margin;
} else {
if (i != 0) {
singleWidth += margin;
}
singleWidth += childWidth;
}
//最后一行
if (i == count - 1) {
maxCalcWidth = Math.max(maxCalcWidth, singleWidth);
}
}
//设置最终高度
setMeasuredDimension(
modeWidth == MeasureSpec.EXACTLY ? sizeWidth : maxCalcWidth,
modeHeight == MeasureSpec.EXACTLY ? sizeHeight : mTotalLength
);
}
onLayout()
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
int count = getChildCount();
int realWidth = r - l - getPaddingLeft() - getPaddingRight();
int left = getPaddingLeft();
int top = getPaddingTop();
int linew = 1;
for (int i = 0; i < count; i++) {
View view = getChildAt(i);
int vw = view.getMeasuredWidth();
int vh = view.getMeasuredHeight();
int vr = left + vw;
if (vr > realWidth) {//超过屏幕了，换行
linew++;
left = getPaddingLeft();
top += vh + margin;
vr = vw;
}
view.layout(left, top, vr, top + vh);
left += vw + margin;//
}
}
其他测试代码
public void addAllTag() {
for (int i = 0; i < contents.length; i++) {
InnerTv tv = new InnerTv(getContext());
LayoutParams lps = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
tv.setText(contents[i]);
tv.setBackgroundColor(Color.GREEN);
tv.setGravity(Gravity.CENTER);
tv.setPadding(10, 5, 10, 5);
addView(tv, lps);
}
}
private String[] contents = new String[]{
"我我我",
"我我我们",
"我我我哦",
"急啊急啊就我",
"我安安",
"我烦烦烦1",
"我烦烦烦2",
"我烦烦烦3",
"我烦烦烦4",
"我烦烦烦55",
"我烦烦烦11",
"我烦烦烦22",
"我烦烦烦33",
"我烦烦烦44",
"我烦烦烦655",
"我烦烦烦666",
"我烦烦烦677",
"我烦烦烦88",
"我烦烦烦99",
"我烦烦烦00"
};
效果图如下
image
简单的tag就实现了，需要圆角的话，只需要给textview添加一个背景即可。
其他扩展
以上效果图，每行都有剩余，能不能让最后一行填满呢。
实际就是让最后一个item,宽度变化
尝试把宽度变长，
修改InnerTv的onMeasure,super.onMeasure 后调用 setMeasuredDimension(reWidth,getMeasuredHeight());
不过效果有点偏差， 那个textview是变宽了，但是文字没居中。。。
TextView的onMeasure中应该已经计算好了文字位置所以这样修改文字没局中
最终实现如下
//上一个重新绘制
int pre = i - 1;
if (pre >= 0) {
InnerTv prev = (InnerTv) getChildAt(pre);
prev.reMeasure(realMaxWidth - singleWidth + prev.getMeasuredWidth());
//重新计算
measureChild(prev, widthMeasureSpec, heightMeasureSpec);
}
InnerTv重写onMeasure
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int width = widthMeasureSpec;
if (reWidth != 0) {
//宽度固定是reWidth，所以模式也强制改成MeasureSpec.EXACTLY，得到新的width
width = MeasureSpec.makeMeasureSpec(reWidth, MeasureSpec.EXACTLY);
}
super.onMeasure(width, heightMeasureSpec);
}
private int reWidth;
public void reMeasure(int width) {
this.reWidth = width;
}
效果图如下：
image
==大功告成==~~~~
说明：这代码只是学习，不够完善，margin都是直接写死的，已经LayoutParams也是不带margin,完善的需要再优化。
完整代码如下：
import android.content.Context;
import android.graphics.Color;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
public class VerticalLinearLayout extends ViewGroup {
public VerticalLinearLayout(Context context) {
super(context);
}
public VerticalLinearLayout(Context context, AttributeSet attrs) {
super(context, attrs);
}
public VerticalLinearLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
measureVertical(widthMeasureSpec, heightMeasureSpec);
}
private int mTotalLength;
private final int margin = 5;
void measureVertical(int widthMeasureSpec, int heightMeasureSpec) {
mTotalLength = 0;
//此处计算的是当前view的大小
int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);
int modeWidth = MeasureSpec.getMode(widthMeasureSpec);
int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);
int modeHeight = MeasureSpec.getMode(heightMeasureSpec);
int count = getChildCount();
//计算每个子类的大小
int maxCalcWidth = 0;//最大宽度，当前view的width为wrap_content时有效
int singleWidth = 0;//当前行宽度
int realMaxWidth = sizeWidth - getPaddingLeft() - getPaddingRight();//去除当前view的padding就是子类可使用的大小
mTotalLength += getPaddingTop() + getPaddingBottom();
for (int i = 0; i < count; i++) {
InnerTv child = (InnerTv) getChildAt(i);//InnerTv继承textView啥都没做,可以不用重写子view的onMeasure。。
if (child == null) {
continue;
}
measureChild(child, widthMeasureSpec, heightMeasureSpec);//计算子view的宽高
int childWidth = child.getMeasuredWidth();
int childHeight = child.getMeasuredHeight();
if (i == 0) {
//首高
mTotalLength += childHeight;// 所有item高度一致，不换行
}
if (singleWidth + childWidth + margin > realMaxWidth) {//超出最大宽度
//上一个重新绘制
int pre = i - 1;
if (pre >= 0) {
InnerTv prev = (InnerTv) getChildAt(pre);
prev.reMeasure(realMaxWidth - singleWidth + prev.getMeasuredWidth());
measureChild(prev, widthMeasureSpec, heightMeasureSpec);
}
//下一行
maxCalcWidth = Math.max(maxCalcWidth, singleWidth);
singleWidth = childWidth;
mTotalLength += childHeight + margin;
} else {
if (i != 0) {
singleWidth += margin;
}
singleWidth += childWidth;
}
//最后一行
if (i == count - 1) {
maxCalcWidth = Math.max(maxCalcWidth, singleWidth);
}
}
//设置最终高度
setMeasuredDimension(
modeWidth == MeasureSpec.EXACTLY ? sizeWidth : maxCalcWidth,
modeHeight == MeasureSpec.EXACTLY ? sizeHeight : mTotalLength
);
}
/**
* 尾部那个长度增加，满屏
*
* @param changed
* @param l
* @param t
* @param r
* @param b
*/
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
int count = getChildCount();
int realWidth = r - l - getPaddingLeft() - getPaddingRight();
int left = getPaddingLeft();
int top = getPaddingTop();
int linew = 1;
for (int i = 0; i < count; i++) {
View view = getChildAt(i);
int vw = view.getMeasuredWidth();
int vh = view.getMeasuredHeight();
int vr = left + vw;
if (vr > realWidth) {
linew++;
left = getPaddingLeft();
top += vh + margin;
vr = vw;
}
view.layout(left, top, vr, top + vh);
left += vw + margin;//
}
}
public void addAllTag() {
for (int i = 0; i < contents.length; i++) {
InnerTv tv = new InnerTv(getContext());
LayoutParams lps = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
tv.setText(contents[i]);
tv.setBackgroundColor(Color.GREEN);
tv.setGravity(Gravity.CENTER);
tv.setPadding(10, 5, 10, 5);
addView(tv, lps);
}
}
private String[] contents = new String[]{
"我我我",
"我我我们",
"我我我哦",
"急啊急啊就我",
"我安安",
"我烦烦烦1",
"我烦烦烦2",
"我烦烦烦3",
"我烦烦烦4",
"我烦烦烦55",
"我烦烦烦11",
"我烦烦烦22",
"我烦烦烦33",
"我烦烦烦44",
"我烦烦烦655",
"我烦烦烦666",
"我烦烦烦677",
"我烦烦烦88",
"我烦烦烦99",
"我烦烦烦00"
};
}
InnerTv
import android.content.Context;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.widget.TextView;
public class InnerTv extends TextView {
public InnerTv(Context context) {
super(context);
}
public InnerTv(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
}
public InnerTv(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int width = widthMeasureSpec;
if (reWidth != 0) {
width = MeasureSpec.makeMeasureSpec(reWidth, MeasureSpec.EXACTLY);
}
super.onMeasure(width, heightMeasureSpec);
}
private int reWidth;
public void reMeasure(int width) {
this.reWidth = width;
}
}
其他
VerticalLinearLayout mf = findViewById(R.id.myflowlayout);
mf.addAllTag();
上面所说到的完善一些， 还会用到另外一个方法
generateDefaultLayoutParams()
返回当前view(父容器) 添加子View时，给子view的默认LayoutParams,以上代码的获取到的getLayoutParams得到的是ViewGroup.LayoutParams,没有margin,所以需要改成MarginLayoutParams
@Override
protected LayoutParams generateDefaultLayoutParams() {
return new MarginLayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
}
该方法的具体实现可以看看FrameLayout、LinearLayout等等常用viewgroup.
//addview没有添加LayoutParams 就会默认生成一个
public void addView(View child, int index) {
if (child == null) {
throw new IllegalArgumentException("Cannot add a null child view to a ViewGroup");
}
LayoutParams params = child.getLayoutParams();
if (params == null) {
params = generateDefaultLayoutParams();
if (params == null) {
throw new IllegalArgumentException("generateDefaultLayoutParams() cannot return null");
}
}
addView(child, index, params);
}
以上就是大概的一个实现过程，动手学习~
最后~~
附上完整版
TagFlowLayout
https://github.com/zeng3234/TagFlowLayout
当然github有很多比较成熟的，比如鸿洋的.. 看哪个顺手用哪个~~
