实现自定义view(1):可在全屏幕自由拖动的view
转自:http://blog.csdn.net/mylzc/article/details/6740877
Android中自带的view种类很多,但是有时候不能满足我们的需求,下面介绍一种自定义view的方法,实现了拖动矩形到屏幕任意位置的需求。
下图为运行效果图:
废话不多说,直接上代码
Activity.java
- package com.zhuozhuo;
- import android.app.Activity;
- import android.os.Bundle;
- public class CSDNActivity extends Activity {
- /** Called when the activity is first created. */
- @Override
- public void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- }
- }
CustomView.java 自定义的view,需要覆盖onDraw()方法绘制控件,覆盖onTouchEvent()接收触摸消息
- package com.zhuozhuo;
- import android.content.Context;
- import android.graphics.Canvas;
- import android.graphics.Color;
- import android.graphics.Paint;
- import android.graphics.Rect;
- import android.util.AttributeSet;
- import android.view.MotionEvent;
- import android.view.View;
- public class CustomView extends View {
- private static final int WIDTH = 40;
- private Rect rect = new Rect(0, 0, WIDTH, WIDTH);//绘制矩形的区域
- private int deltaX,deltaY;//点击位置和图形边界的偏移量
- private static Paint paint = new Paint();//画笔
- public CustomView(Context context, AttributeSet attrs) {
- super(context, attrs);
- paint = new Paint();
- paint.setColor(Color.RED);//填充红色
- }
- @Override
- protected void onDraw(Canvas canvas) {
- canvas.drawRect(rect, paint);//画矩形
- }
- @Override
- public boolean onTouchEvent (MotionEvent event) {
- int x = (int) event.getX();
- int y = (int) event.getY();
- switch(event.getAction()) {
- case MotionEvent.ACTION_DOWN:
- if(!rect.contains(x, y)) {
- return false;//没有在矩形上点击,不处理触摸消息
- }
- deltaX = x - rect.left;
- deltaY = y - rect.top;
- break;
- case MotionEvent.ACTION_MOVE:
- case MotionEvent.ACTION_UP:
- Rect old = new Rect(rect);
- //更新矩形的位置
- rect.left = x - deltaX;
- rect.top = y - deltaY;
- rect.right = rect.left + WIDTH;
- rect.bottom = rect.top + WIDTH;
- old.union(rect);//要刷新的区域,求新矩形区域与旧矩形区域的并集
- invalidate(old);//出于效率考虑,设定脏区域,只进行局部刷新,不是刷新整个view
- break;
- }
- return true;//处理了触摸消息,消息不再传递
- }
- }
- <?xml version="1.0" encoding="utf-8"?>
- <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
- android:orientation="vertical"
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- >
- <com.zhuozhuo.CustomView android:layout_width="fill_parent"
- android:layout_height="fill_parent"/>
- </LinearLayout>
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