图片的画画板

布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >


    <Button
        android:onClick="selectImage"
        android:id="@+id/button1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="选择图片" />
    <Button
        android:onClick="saveImage"
        android:id="@+id/button1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="保存图片" />
    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:scaleType="centerInside"
        android:id="@+id/iv" />
</LinearLayout>

项目代码

package cn.itcast.paint;

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

import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Bitmap.CompressFormat;
import android.graphics.BitmapFactory.Options;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Rect;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.view.Display;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.WindowManager;
import android.widget.ImageView;
import android.widget.Toast;

public class DemoActivity extends Activity {
    private ImageView iv;
    private Bitmap alterBitmap;
    private Canvas canvas;
    private Paint paint;
    private WindowManager wm;
    private Display  display;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        iv = (ImageView) findViewById(R.id.iv);
        paint = new Paint();
        paint.setColor(Color.GREEN);
        paint.setStrokeWidth(10);
        wm = getWindowManager();
        //获取手机的屏幕宽高
        display = wm.getDefaultDisplay();
        iv.setOnTouchListener(new OnTouchListener() {
            int startx;
            int starty;
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN://手指第一次触摸屏幕
                    startx = (int) event.getX();
                    starty = (int) event.getY();
                    
                    break;
                case MotionEvent.ACTION_MOVE: //手指在imageview上中移动
                    int x = (int) event.getX();
                    int y = (int) event.getY();
                    canvas.drawLine(startx, starty, x, y, paint);
                    startx = (int) event.getX();
                    starty = (int) event.getY();
                    iv.invalidate();
                    break;
                }
                
                
                
                return true;
            }
        });
    }
    
    
    public void selectImage(View view){
        Intent intent = new Intent();
        intent.setAction(Intent.ACTION_PICK);
        intent.addCategory("android.intent.category.DEFAULT");
        intent.setType("image/*");
        startActivityForResult(intent, 0);
    }
    
    
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        try {
            if (data != null) {
                // 得到点击图片的uri
                Uri uri = data.getData();
                //对 要加载的图片进行缩放
                //1.得到图片的宽度和高度.
                //由于我们只想得到图片的宽度和高度,这个时候 只需要解析图片的头信息
                BitmapFactory.Options opts = new Options();
                opts.inJustDecodeBounds = true;//让 bimapfactory假的解析这个位图,只获取位图的边框信息
                InputStream is = getContentResolver().openInputStream(uri);
                BitmapFactory.decodeStream(is, new Rect(), opts);
                
                int bitmapHeight =     opts.outHeight;
                int bitmapWidth = opts.outWidth;
                
                int windowHeight = display.getHeight();
                int windowWidth = display.getWidth();
                //获取水平和垂直方向的缩放比
                int scaley = bitmapHeight / windowHeight;
                int scalex = bitmapWidth / windowWidth;
                
                
                
                if(scalex>scaley&&scaley>1){
                    opts.inSampleSize = scalex;
                }
                if(scaley>scalex&&scalex>1){
                    opts.inSampleSize = scaley;
                }
                opts.inJustDecodeBounds = false;// 由于已经得到了缩放比例 ,让位图工厂真正的解析这个位图
                // 由于前面 我们已经解析了这个输入流, 需要重新初始化这个输入流
                is = getContentResolver().openInputStream(uri);
                Bitmap bitmap =  BitmapFactory.decodeStream(is, new Rect(), opts);
                System.out.println("位图的高度:"+bitmap.getHeight());
                System.out.println("位图的宽度:"+bitmap.getWidth());
                
                
                alterBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), bitmap.getConfig());
                
                canvas = new Canvas(alterBitmap);
                
                canvas.drawBitmap(bitmap, new Matrix(), new Paint());
                
                //设置的是原图在内存中的拷贝
                iv.setImageBitmap(alterBitmap);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        super.onActivityResult(requestCode, resultCode, data);
    }
    
    public void saveImage(View view){
        try {
            File file = new File(Environment.getExternalStorageDirectory(),System.currentTimeMillis()+".jpg");
            FileOutputStream stream = new FileOutputStream(file);
            alterBitmap.compress(CompressFormat.JPEG, 100, stream);
            Toast.makeText(this, "保存成功", 1).show();
            // 模拟系统发送一个 sd卡挂载的广播 
            Intent intent = new Intent();
            intent.setAction(Intent.ACTION_MEDIA_MOUNTED);
            intent.setData(Uri.parse("file:"+Environment.getExternalStorageDirectory().getAbsolutePath()));
            sendBroadcast(intent); 
        } catch (FileNotFoundException e) {
            Toast.makeText(this, "保存失败", 1).show();
            e.printStackTrace();
        }
    }
}