组件拖动显示

这里可以像悬浮显示可拖动的歌词栏
一样自定义组件重写onTouchEvent方法然后再重写onDraw方法来绘制，也可以在activity中重写onTouch事件，比较简单，代码如下：

MainActivity：

package com.home.drafttest;

import android.app.Activity;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.Button;

public class MainActivity extends Activity {
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		// 获取屏幕宽高
		DisplayMetrics dm = getResources().getDisplayMetrics();
		final int screenWidth = dm.widthPixels;
		final int screenHeight = dm.heightPixels - 50;

		final Button btn = (Button) findViewById(R.id.main_btn);
		btn.setOnTouchListener(new OnTouchListener() {
			// 组件位置
			int lastX, lastY;

			@Override
			public boolean onTouch(View v, MotionEvent event) {
				int ea = event.getAction();
				switch (ea) {
				case MotionEvent.ACTION_DOWN:
					lastX = (int) event.getRawX();
					lastY = (int) event.getRawY();
					break;
				case MotionEvent.ACTION_MOVE:
					int dx = (int) event.getRawX() - lastX;
					int dy = (int) event.getRawY() - lastY;

					int left = v.getLeft() + dx;
					int top = v.getTop() + dy;
					int right = v.getRight() + dx;
					int bottom = v.getBottom() + dy;

					if (left < 0) {
						left = 0;
						right = left + v.getWidth();
					}
					if (right > screenWidth) {
						right = screenWidth;
						left = right - v.getWidth();
					}
					if (top < 0) {
						top = 0;
						bottom = top + v.getHeight();
					}
					if (bottom > screenHeight) {
						bottom = screenHeight;
						top = bottom - v.getHeight();
					}
					v.layout(left, top, right, bottom);
					lastX = (int) event.getRawX();
					lastY = (int) event.getRawY();
					break;
				case MotionEvent.ACTION_UP:
					break;
				}
				return false;
			}
		});
	}
}