Question

安卓编程中如何判断View之间的碰撞

Answer 1

View的移动和碰撞检测的核心就在于如何获取到View在屏幕中的位置，获取的方法很多，本文中直接使用View.getX() View.getY()方法获取到左上角的顶点位置，View之间的碰撞检测就是在View的移动过程中不断计算和特定View之间的距离。代码如下：

import android.content.Context;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.RelativeLayout;

public class TouchMoveView extends RelativeLayout {
private static final String TAG="TouchMoveView";
private View mTargetView;
private View mRedView, mBlueView, mGreenView, mYellowView;
private RectF mRedRect,mBlueRect,mGreenRect,mYellowRect,mTargetRect;

private View mParentView;
public TouchMoveView(Context context) {
this(context, null);
}

public TouchMoveView(Context context, AttributeSet attrs) {
super(context, attrs);
}

@Override
protected void onFinishInflate() {
super.onFinishInflate();
mTargetView = findViewById(R.id.target_view);
mRedView = findViewById(R.id.red);
mBlueView = findViewById(R.id.blue);
mGreenView = findViewById(R.id.green);
mYellowView = findViewById(R.id.yellow);

mParentView=findViewById(R.id.parent_view);
}

private View mTouchedView;
private float mInitX;
private float mInitY;
@Override
public boolean onTouchEvent(MotionEvent event) {
initRect();
float x=event.getX();
float y=event.getY();
int action=event.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN:
mTouchedView=getTouchedView((int)x, (int)y);
if(null!=mTouchedView){
mInitX=mTouchedView.getX();
mInitY=mTouchedView.getY();
}
Log.e(TAG,"mTouchedView:"+mTouchedView);
return true;
case MotionEvent.ACTION_MOVE:
if(null!=mTouchedView){
float moveX=x-mTouchedView.getWidth()/2;
float moveY=y-mTouchedView.getHeight()/2;
Log.e(TAG,"moveX:"+moveX+" moveY:"+moveY );
mTouchedView.setX(moveX);
mTouchedView.setY(moveY);

if(isTwoViewClose(mTouchedView, mTargetView)){
int colorRes=getColorRes(mTouchedView);
mTargetView.setBackgroundColor(getResources().getColor(colorRes));
}else{
mTargetView.setBackgroundColor(getResources().getColor(R.color.black));
}
}
return true;

case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
if(null!=mTouchedView){
mTouchedView.setX(mInitX);
mTouchedView.setY(mInitY);
}
mTargetView.setBackgroundColor(getResources().getColor(R.color.black));
return true;
default:
return false;
}
}
private int getColorRes(View view){
if(null==view){
return R.color.black;
}
int id=view.getId();
switch (id) {
case R.id.blue:
return R.color.blue;
case R.id.red:
return R.color.red;
case R.id.green:
return R.color.green;
case R.id.yellow:
return R.color.yellow;
default:
return R.color.black;
}
}

private View getTouchedView(int x,int y){
Log.e(TAG,"x:"+x+" y:"+y);
Log.e(TAG,"mRedRect"+mRedRect);
Log.e(TAG,"mBlueRect"+mBlueRect);
Log.e(TAG,"mGreenRect"+mGreenRect);
Log.e(TAG,"mYellowRect"+mYellowRect);
if(mRedRect.contains(x, y)){
return mRedView;
}

if(mBlueRect.contains(x, y)){
return mBlueView;
}

if(mGreenRect.contains(x, y)){
return mGreenView;
}

if(mYellowRect.contains(x, y)){
return mYellowView;
}
return null;

}
private void initRect(){
if(null==mRedRect){
mRedRect=getRect(mRedView);
}

if(null==mBlueRect){
mBlueRect=getRect(mBlueView);
}
if(null==mGreenRect){
mGreenRect=getRect(mGreenView);
}
if(null==mYellowRect){
mYellowRect=getRect(mYellowView);
}
if(null==mTargetRect){
mTargetRect=getNormalRect(mTargetView);
}
}
private RectF getNormalRect(View view){
return new RectF(view.getX(),view.getY(),view.getX()+view.getWidth(),view.getY()+view.getHeight());
}

private RectF getRect(View view){
RectF rectf=new RectF(view.getX(),view.getY()+mParentView.getY(),view.getX()+view.getWidth(),view.getY()+mParentView.getY()+view.getHeight());
return rectf;
}
/**判断两个View是否相交
* @param src
* @param target
* @return
*/
private boolean isTwoViewClose(View src,View target){
RectF rectSrc=getNormalRect(src);
RectF rectTar=getNormalRect(target);
return rectSrc.intersect(rectTar);
}