1. 数组元素总是莫名丢失？说不定是这个原因
(1)数组list2所有元素都赋值给list1，地址一样。list1修改元素，list2也会对应跟着修改。
list1 = list2;
(2) 数组list2所有元素都赋值给list1，地址不一样。两个数组互不影响。
list1.clear();
list1.addAll(list2);
用第二种解决问题。
2. java.lang.IllegalStateException: Timer was canceled
不妨使用以下代码
if (timer != null) {
timer.cancel();
timer.purge();
timer = null; // (可选)
}
3. java.lang.IllegalStateException: TimerTask is scheduled already
试试这招
if (mTimerTask != null){
mTimerTask.cancel(); // 将原任务从队列中移除
}
mTimerTask = new MyTimerTask(); // 新建一个任务
mTimer.schedule(mTimerTask, 3000);
4. Listview实现多种adapter布局方式容易忽略的点
- getView函数中convertView==null时没有设置setTag
public View getView(int position, View convertView, ViewGroup parent) {
ViewRecord viewRecord = null;
ViewPhase viewPhase = null;
int type = getItemViewType(position);
if (convertView == null) {
inflater = LayoutInflater.from(mContext);
if (type == Type_record) {
convertView = inflater.inflate(R.layout.live_study_record_layout, parent, false);
viewRecord = new ViewRecord();
viewRecord.firstTime = (TextView) convertView.findViewById(R.id.live_study_record_first_time);
convertView.setTag(viewRecord);
} else {
convertView = inflater.inflate(R.layout.live_study_item_layout, parent, false);
viewPhase = new ViewPhase();
viewPhase.title = (TextView) convertView.findViewById(R.id.live_study_item_title);
convertView.setTag(viewPhase);
}
} else {
if (type == Type_record) {
viewRecord = (ViewRecord) convertView.getTag();
} else {
viewPhase = (ViewPhase) convertView.getTag();
}
}
}
- getItemViewType函数需从零开始赋值，并且getViewTypeCount > getItemViewType，如下2 > 1。
private static final int Type_record = 0;
private static final int Type_phase = 1;
public int getItemViewType(int position) {
if (position == 0) {
return Type_record;
} else {
return Type_phase;
}
}
public int getViewTypeCount() {
return 2;
}
5. 上、下、左、右滑动手势识别以及子控件挡住手势的处理。
1. 添加手势
public class GameActivity extends AppCompatActivity implements android.view.GestureDetector.OnGestureListener
//定义手势检测器实例
GestureDetector detector;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//创建手势检测器
detector = new GestureDetector(this, this);
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
float minMove = 0; //最小滑动距离，可根据需求自定义设置
float minVelocity = 0; //最小滑动速度，demo未使用，可根据需求添加该判断
float beginX = e1.getX();
float endX = e2.getX();
float beginY = e1.getY();
float endY = e2.getY();
if (beginX-endX > minMove && Math.abs(beginY-endY) < Math.abs(beginX-endX)) {
Log.e(TAG, "左滑");
} else if (beginX-endX < minMove && Math.abs(beginY-endY) < Math.abs(beginX-endX)) {
Log.e(TAG, "右滑");
} else if (beginY-endY > minMove && Math.abs(beginY-endY) > Math.abs(beginX-endX)) {
Log.e(TAG, "上滑");
} else if (beginY-endY < minMove && Math.abs(beginY-endY) > Math.abs(beginX-endX)) {
Log.e(TAG, "下滑");
}
return false;
}
滑动手势可能为左上、右下这样包含两个方向属性，所以做左右和上下滑动距离绝对值的大小判断，大的则为该滑动手势的方向。
2. 子控件挡住滑动手势的处理
为该子控件也添加上setOnTouchListener：
btn.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
return detector.onTouchEvent(event);
}
});
6. substring（beginIndex,endIndex）
begingIndex：包括
endIndex：不包括。
用数学的表达方式为 [begingIndex, endIndex)
"abcdefg".substring(2,4)
returns "cd"
7.Plugin Error: required plugin “Android Support” is disabled
更详细的错误信息如下：
Plugin "Google Analytics Uploader" was not loaded: required plugin "Android Support" is disabled.
Plugin "SDK Updater" was not loaded: required plugin "Android Support" is disabled.
Plugin "Android NDK Support" was not loaded: required plugin "Android Support" is disabled.
Plugin "Google App Indexing" was not loaded: required plugin "Android Support" is disabled.
Plugin "Google Cloud Tools For Android Studio" was not loaded: required plugin "Android Support" is disabled.
Plugin "Google Cloud Testing" was not loaded: required plugin "Android Support" is disabled.
Plugin "Google Services" was not loaded: required plugin "Android Support" is disabled.
解决方法：
依次点击菜单“File”——“Settings”——“Plugins”，可看到“Android Support”被取消勾选了。此时按如下步骤操作，先取消勾选其中一项，然后再勾选“Android Support”，单击“Apply”按钮后再单击“OK”按钮，Android Studio会提示重启，重启Android Studio，然后就恢复正常了。
