Android开发之触摸事件的使用--触…

.xml文件

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical"

    tools:context=".MainActivity" >

 

    <com.example.touchproject2.MyPaintView

        android:id="@+id/paintView"

        android:layout_width="fill_parent"

        android:layout_height="fill_parent"/>

</LinearLayout>

MainActivity.java文件

package com.example.touchproject2;

import android.os.Bundle;

import android.app.Activity;

import android.view.Menu;

public class MainActivity extends Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

// Inflate the menu; this adds items to the action bar if it is present.

getMenuInflater().inflate(R.menu.activity_main, menu);

return true;

}

}

MyPaintView.java文件

package com.example.touchproject2;

import java.util.ArrayList;

import java.util.Iterator;

import java.util.List;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Point;

import android.util.AttributeSet;

import android.view.MotionEvent;

import android.view.View;

public class MyPaintView extends View {

private List<Point> allPoints=new ArrayList<Point>();

//接受context以及属性集合(宽度，高度等)

public MyPaintView(Context context, AttributeSet attrs) {

super(context, attrs);

super.setOnTouchListener(new OnTouchListenerImp());

}

private class OnTouchListenerImp implements OnTouchListener{

public boolean onTouch(View v, MotionEvent event) {

Point p=new Point((int)event.getX(),(int)event.getY());

if(event.getAction()==MotionEvent.ACTION_DOWN){

//用户按下，表示重新开始保存点

MyPaintView.this.allPoints=new ArrayList<Point>();

MyPaintView.this.allPoints.add(p);

}

else if(event.getAction()==MotionEvent.ACTION_UP){

//用户松开

MyPaintView.this.allPoints.add(p);

MyPaintView.this.postInvalidate();//重绘图像

}

else if(event.getAction()==MotionEvent.ACTION_MOVE){

MyPaintView.this.allPoints.add(p);

MyPaintView.this.postInvalidate();//重绘图像

}

return true;

}

}

@Override

public void draw(Canvas canvas) {

Paint p=new Paint();//依靠此类开始画线

p.setColor(Color.RED);

if(MyPaintView.this.allPoints.size()>1){

//如果有坐标点，开始绘图

Iterator<Point> iter=MyPaintView.this.allPoints.iterator();

Point first=null;

Point last=null;

while(iter.hasNext()){

if(first==null){

first=(Point)iter.next();

}else{

if(last!=null){

first=last;

}

last=(Point)iter.next();//结束

canvas.drawLine(first.x, first.y, last.x, last.y, p);

}

}

}

}

}