android多媒体编程--画画板

package com.example.huahuaban;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;

import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.Bitmap.CompressFormat;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.ImageView;

public class MainActivity extends Activity implements OnClickListener{
private ImageView img;
Bitmap bitmapcopy;
Paint paint;
Bitmap bitmapsrc ;
float startx =0;
float starty = 0;
private Canvas canvas;
private Matrix mt;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
img = (ImageView) findViewById(R.id.img);
findViewById(R.id.red).setOnClickListener(this);
findViewById(R.id.gereen).setOnClickListener(this);
findViewById(R.id.blue).setOnClickListener(this);
findViewById(R.id.shua).setOnClickListener(this);
findViewById(R.id.qingkong).setOnClickListener(this);
findViewById(R.id.save).setOnClickListener(this);
bitmapsrc = BitmapFactory.decodeResource(getResources(), R.drawable.bg);
bitmapcopy = Bitmap.createBitmap(bitmapsrc.getWidth(), bitmapsrc.getHeight(), bitmapsrc.getConfig());
//画笔
paint = new Paint();
canvas = new Canvas(bitmapcopy);
mt = new Matrix();
canvas.drawBitmap(bitmapsrc, mt, paint);

img.setOnTouchListener(new OnTouchListener() {

@Override
public boolean onTouch(View arg0, MotionEvent event) {
int action = event.getAction();

switch (action) {
case MotionEvent.ACTION_DOWN:
//设置线段的开始坐标
startx = event.getX();
starty = event.getY();
break;
case MotionEvent.ACTION_MOVE:
//结束坐标
float x =  event.getX();
float y =  event.getY();

canvas.drawLine(startx, starty, x, y, paint);
img.setImageBitmap(bitmapcopy);
//把结束坐标的值赋给开始坐标
startx = x;
starty = y;
break;
case MotionEvent.ACTION_UP:

break;

}
return true;
}
});
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.red:
paint.setColor(Color.RED);
break;
case R.id.gereen:
paint.setColor(Color.GREEN);
break;
case R.id.blue:
paint.setColor(Color.BLUE);
break;
case R.id.qingkong:
paint.setXfermode(new PorterDuffXfermode(Mode.CLEAR));
canvas.drawBitmap(bitmapsrc, mt, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC));
img.invalidate();
break;
case R.id.shua:
paint.setStrokeWidth(3.5f);
break;
case R.id.save:
File file = new File("sdcard/ok1.png");
FileOutputStream out = null;
try {
out = new FileOutputStream(file);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//保存文件，参数分别为格式，压缩质量0-100，输出流
bitmapcopy.compress(CompressFormat.PNG, 100, out);
//发送更新多媒体数据库的广播
Intent intent = new Intent();
intent.setAction(Intent.ACTION_MEDIA_MOUNTED);
intent.setData(Uri.fromFile(Environment.getExternalStorageDirectory()));
sendBroadcast(intent);
break;

}

}

}

<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"

tools:context=".MainActivity"
android:orientation="vertical">

<ImageView
android:id="@+id/img"
android:layout_width="wrap_content"
android:layout_height="wrap_content"

android:src="@drawable/bg"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
>
<Button
android:id="@+id/red"
android:background="#FF0000"
android:layout_width="wrap_content"
android:layout_height="wrap_content"

/>
<Button
android:id="@+id/gereen"
android:background="#00FF00"
android:layout_width="wrap_content"
android:layout_height="wrap_content"

/>
<Button
android:id="@+id/blue"
android:background="#3366FF"
android:layout_width="wrap_content"
android:layout_height="wrap_content"

/>
<Button
android:id="@+id/shua"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="加粗"
/>
<Button
android:id="@+id/qingkong"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="清空"
/>
</LinearLayout>
<Button
android:id="@+id/save"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="保存"
/>

</LinearLayout>