android 图片画画板

canvas.xml：

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:orientation="vertical"
        >
    <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="保存"
            android:onClick="save"
            />

    <ImageView
            android:id="@+id/image"
            android:layout_width="480px"
            android:layout_height="320px"
            />
</LinearLayout>

package com.example.imageLoadBigImg;

import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;

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

/**
 * 图片画板
 * Created by Heyiyong on 2014-4-11 下午1:58.
 */
public class ImageCanvasActivity extends Activity {

    private ImageView imageView;
    private Bitmap bitmap;
    private Canvas canvas;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.canvas);

        imageView = (ImageView) findViewById(R.id.image);

        //创建画笔样式
        final Paint paint = new Paint();
        paint.setColor(Color.RED);

        //创建一个可修改的bitmap
        bitmap = Bitmap.createBitmap(480, 320, Bitmap.Config.ARGB_4444);

        //以bitmap为模板，创建画板对象
        canvas = new Canvas(bitmap);
        canvas.drawColor(Color.WHITE);

        imageView.setOnTouchListener(new View.OnTouchListener() {
            int startX;
            int startY;

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                switch (event.getAction()) {
                    case MotionEvent.ACTION_DOWN://按下的时候
                        startX = (int) event.getX();
                        startY = (int) event.getY();
                        break;
                    case MotionEvent.ACTION_MOVE://移动的时候

                        int newX = (int) event.getX();
                        int newY = (int) event.getY();
                        canvas.drawLine(startX, startY, newX, newY, paint);
                        //重置初始位置
                        startX = newX;
                        startY = newY;
                        //将画板的图片设置上去
                        imageView.setImageBitmap(bitmap);
                        break;
                    case MotionEvent.ACTION_UP://手放开的时候
                        break;
                }
                return true;
            }
        });
    }

    public void save(View view) {
        try {
            File file = new File(Environment.getExternalStorageDirectory(), System.currentTimeMillis() + ".jpg");
            FileOutputStream fos = new FileOutputStream(file);
            bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);//第一个参数为图片格式
            fos.close();
            Toast.makeText(this, "保存图片成功", 2000).show();
            //模拟消息：SD卡被重新挂载了
            Intent intent = new Intent();
            intent.setAction(intent.ACTION_MEDIA_MOUNTED);
            intent.setData(Uri.fromFile(Environment.getExternalStorageDirectory()));
            sendBroadcast(intent);
        } catch (FileNotFoundException e) {
            Toast.makeText(this, "保存图片失败", 2000).show();
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}