Android开发之触摸事件的使用--触…

.xml文件

<LinearLayoutxmlns: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

packagecom.example.touchproject2;

importandroid.os.Bundle;

importandroid.app.Activity;

importandroid.view.Menu;

public class MainActivityextends Activity {

@Override

protected void onCreate(BundlesavedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

}

@Override

public booleanonCreateOptionsMenu(Menu menu) {

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

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

return true;

}

}

MyPaintView.java文件

packagecom.example.touchproject2;

importjava.util.ArrayList;

importjava.util.Iterator;

importjava.util.List;

importandroid.content.Context;

importandroid.graphics.Canvas;

importandroid.graphics.Color;

importandroid.graphics.Paint;

importandroid.graphics.Point;

importandroid.util.AttributeSet;

importandroid.view.MotionEvent;

importandroid.view.View;

public class MyPaintViewextends View {

privateList<Point> allPoints=newArrayList<Point>();

//接受context以及属性集合(宽度，高度等)

public MyPaintView(Contextcontext, AttributeSet attrs) {

super(context,attrs);

super.setOnTouchListener(newOnTouchListenerImp());

}

private classOnTouchListenerImp implements OnTouchListener{

public boolean onTouch(View v,MotionEvent event) {

Point p=newPoint((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=newArrayList<Point>();

MyPaintView.this.allPoints.add(p);

}

elseif(event.getAction()==MotionEvent.ACTION_UP){

//用户松开

MyPaintView.this.allPoints.add(p);

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

}

elseif(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=newPaint();//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);

}

}

}

}

}