android，添加多个ImageViews onTouch事件

Question

我刚刚开始为Android编程。我已经搜索了很多我的问题，但建议对我没有帮助。我希望在屏幕上的触摸坐标中出现相同的图像。这就是我所做的：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    View main_view = (View)findViewById(R.id.main_view);
    main_view.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            ImageView image = new ImageView(getApplicationContext());
            //ImageView image = (ImageView)findViewById(R.id.broken);
            image.setImageResource(R.drawable.broken);
            image.setX(event.getX() + image.getWidth() / 2);
            image.setY(event.getY() - image.getHeight() / 2);
            LinearLayout top_layout = (LinearLayout) findViewById(R.id.top_layout);
            LayoutParams p = new LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
            image.setLayoutParams(p);
            top_layout.addView(image);
            return true;
        }
    });
}

在我看来一切都很好，但当触摸屏幕时，什么也没发生。我犯的明显错误在哪里？提前谢谢。

Answer 1

在LinearLayout中不能这样做。让我们使用FrameLayout。

activity_main.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/framelayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
</FrameLayout>

MainActivity.java

public class MainActivity extends Activity {
    private FrameLayout mLayout;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mLayout = (FrameLayout) findViewById(R.id.framelayout);
        mLayout.setOnTouchListener(mListener);
    }
    private OnTouchListener mListener = new OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                return true;
            case MotionEvent.ACTION_UP:
                // decode the resource to get width and height
                Options opts = new Options();
                opts.inJustDecodeBounds = true;
                BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher, opts);
                int imageWidth = opts.outWidth;
                int imageHeight = opts.outHeight;
                // set the imageview's top and left margins
                FrameLayout.LayoutParams lp = new LayoutParams(imageWidth, imageHeight);
                lp.leftMargin = (int) (event.getX() - (imageWidth / 2));
                lp.topMargin = (int) (event.getY() - (imageHeight / 2));
                ImageView image = new ImageView(MainActivity.this);
                image.setImageResource(R.drawable.ic_launcher);
                mLayout.addView(image, lp);
                return false;
            }
            return false;
        }
    };
}

Answer 2

setX和setY不设置图像位置。它基本上将图像滚动到位。位置由其父视图控制。由于它的父对象是线性布局，因此在布局中，它将始终放置在它上面的东西的下面或右边。如果你想把它准确地放在某个地方，你需要把它放在一个支持它的父级中，比如不推荐使用的AbsoluteLayout。