Android 自定义LineLayout实现满屏任意拖动功能的示例代码

1.前言

在开发中，会有需求实现控件在屏幕随意拖动，这就需要自定义View,然后在OnTouchEvent事件中，处理MotionEvent.ACTION_MOVE事件，然后通过坐标点传值给onlayout方法,来实现控件的任意拖动，具体代码如下：

import android.content.Context;
import android.util.AttributeSet;
import android.view.Display;
import android.view.MotionEvent;
import android.view.WindowManager;
import android.widget.LinearLayout;

public class DragLineLayout extends LinearLayout {

 private int mWidth;
 private int mHeight;
 private int mScreenWidth;
 private int mScreenHeight;
 private Context mContext;
 private onLocationListener mLocationListener;/*listen to the Rect */
 //是否拖动
 private boolean isDrag = false;

 public boolean isDrag() {
  return isDrag;
 }

 public DragView(Context context, AttributeSet attrs) {
  super(context, attrs);
  this.mContext = context;
 }

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  mWidth = getMeasuredWidth();
  mHeight = getMeasuredHeight();
  mScreenWidth = getScreenWidth(mContext);
  mScreenHeight = getScreenHeight(mContext) - getStatusBarHeight();
 }

 public int getStatusBarHeight() {
  int resourceId = mContext.getResources().getIdentifier("status_bar_height", "dimen", "android");
  return mContext.getResources().getDimensionPixelSize(resourceId);
 }

 public int getScreenWidth(Context context) {
  WindowManager manager = (WindowManager) context
    .getSystemService(Context.WINDOW_SERVICE);
  Display display = manager.getDefaultDisplay();
  return display.getWidth();
 }

 public int getScreenHeight(Context context) {
  WindowManager manager = (WindowManager) context
    .getSystemService(Context.WINDOW_SERVICE);
  Display display = manager.getDefaultDisplay();
  return display.getHeight();
 }

 private float mDownX;
 private float mDownY;


 @Override
 public boolean onTouchEvent(MotionEvent event) {
  super.onTouchEvent(event);
  if (this.isEnabled()) {
   switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
     isDrag = false;
     mDownX = event.getX();
     mDownY = event.getY();
     break;
    case MotionEvent.ACTION_MOVE:
     final float mXdistance = event.getX() - mDownX;
     final float mYdistance = event.getY() - mDownY;
     int l, r, t, b;
     //当水平或者垂直滑动距离大于10,才算是拖动事件
     if (Math.abs(mXdistance) > 10 || Math.abs(mYdistance) > 10) {
      isDrag = true;
      l = (int) (getLeft() + mXdistance);
      r = l + mWidth;
      t = (int) (getTop() + mYdistance);
      b = t + mHeight;
      //边界判断,不让布局滑出界面
      if (l < 0) {
       l = 0;
       r = l + mWidth;
      } else if (r > mScreenWidth) {
       r = mScreenWidth;
       l = r - mWidth;
      }
      if (t < 0) {
       t = 0;
       b = t + mHeight;
      } else if (b > mScreenHeight) {
       b = mScreenHeight;
       t = b - mHeight;
      }
      //回调移动后的坐标点
      if(mLocationListener!=null){
       mLocationListener.locationRect((l+r)/2,(t+b)/2);
      }
      this.layout(l, t, r, b);
     }
     break;
    case MotionEvent.ACTION_UP:
     setPressed(false);
     break;
    case MotionEvent.ACTION_CANCEL:
     setPressed(false);
     break;
   }
   return true;
  }
  return false;
 }
 public void setLocationListener(onLocationListener LocationListener) {
  this.mLocationListener = LocationListener;
 }
 public interface onLocationListener {
  void locationRect(float locationX, float locationY);
 }
}

2.在代码中的运用

3.这样就可以在Activity 加载这个xml 来实现任意拖动功能

总结

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