android中碰撞屏幕边界反弹问题

其实碰撞问题只是涉及到一点小算法而已，但在实际应用，尤其游戏中有可能会遇到，下面给出一个小示例，代码如下：

MainActivity：

package com.lovo;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.app.Activity;

public class MainActivity extends Activity {
    private Handler handler;
    public static final int MOVE_IMAGE = 1;
    // 移动方向和距离
    private int decX = 5;
    private int decY = 5;
    // 坐标
    private int moveX;
    private int moveY;
    private boolean isMove;// 是否正在移动
    private RelativeLayout relative;
    private ImageView imageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imageView = (ImageView) findViewById(R.id.activity_main_image);
        handler = new MyHandler(this);
        relative = (RelativeLayout) findViewById(R.id.activity_main_relativelayout);
        Button endBtn = (Button) findViewById(R.id.activity_main_btn_end);
        endBtn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                isMove = false;
            }
        });
        Button btn = (Button) findViewById(R.id.activity_main_btn_start);
        btn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                if (!isMove) {
                    isMove = true;
                } else {
                    return;
                }
                new Thread() {
                    public void run() {
                        while (isMove) {
                            moveX += decX;
                            moveY += decY;
                            if ((moveX + imageView.getWidth()) >= relative
                                    .getWidth() || moveX < 0) {
                                decX = -decX;
                            }
                            if ((moveY + imageView.getHeight()) >= relative
                                    .getHeight() || moveY < 0) {
                                decY = -decY;
                            }
                            Message message = new Message();
                            message.what = MOVE_IMAGE;

                            Bundle bundle = new Bundle();
                            bundle.putInt("moveX", moveX);
                            bundle.putInt("moveY", moveY);
                            message.setData(bundle);
                            handler.sendMessage(message);
                            try {
                                Thread.sleep(10);
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                    };
                }.start();
            }
        });
    }

}

MyHandler类：

package com.lovo;

import android.app.Activity;
import android.os.Handler;
import android.os.Message;
import android.widget.ImageView;
import android.widget.RelativeLayout;

public class MyHandler extends Handler {
    private Activity activity;
    private ImageView imageView;

    public MyHandler(Activity activity) {
        this.activity = activity;
    }

    @Override
    public void handleMessage(Message msg) {
        super.handleMessage(msg);
        imageView = (ImageView) activity.findViewById(R.id.activity_main_image);
        if (msg.what == MainActivity.MOVE_IMAGE) {
            android.widget.RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
                    RelativeLayout.LayoutParams.WRAP_CONTENT,
                    RelativeLayout.LayoutParams.WRAP_CONTENT);
            // 利用Margin改变小球的位置
            lp.setMargins(msg.getData().getInt("moveX"),
                    msg.getData().getInt("moveY"), 0, 0);
            imageView.setLayoutParams(lp);
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/activity_main_relativelayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true" >

        <Button
            android:id="@+id/activity_main_btn_start"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="开始" />

        <Button
            android:id="@+id/activity_main_btn_end"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="停止" />
    </LinearLayout>

    <ImageView
        android:id="@+id/activity_main_image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ball" />

</RelativeLayout>

附上图片效果：