android 画画板

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.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.SweepGradient;
import android.view.Menu;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.ImageView;
import android.widget.Toast;


public class MainActivity extends Activity {
private ImageView iv;
private Bitmap baseBitmap;
private Canvas canvas;
private Paint paint;


@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
iv = (ImageView) findViewById(R.id.iv);
paint = new Paint();
paint.setStrokeWidth(5);
paint.setColor(Color.GREEN);

// 创建一个可以被修改的bitmap
baseBitmap = Bitmap.createBitmap(320, 359,
Bitmap.Config.ARGB_8888);
System.out.println("图宽度:"+iv.getWidth());
System.out.println("图宽高:"+iv.getHeight());
canvas = new Canvas(baseBitmap);
canvas.drawColor(Color.WHITE);


// 知道用户手指在屏幕上移动的轨迹
iv.setOnTouchListener(new OnTouchListener() {
//定义手指开始位置的坐标
int startX;
int startY;
@Override
public boolean onTouch(View v, MotionEvent event) {


switch (event.getAction()) {
case MotionEvent.ACTION_DOWN: // 手指第一次接触屏幕
System.out.println("手指按下");

startX = (int) event.getX();
startY = (int) event.getY();
break;
case MotionEvent.ACTION_MOVE: // 手指在屏幕上滑动
System.out.println("手指移动");
int newX  = (int) event.getX();
int newY = (int) event.getY();

canvas.drawLine(startX,startY, newX, newY, paint);
//重新更新画笔的开始位置.
startX = (int) event.getX();
startY = (int) event.getY();
iv.setImageBitmap(baseBitmap);
break;
case MotionEvent.ACTION_UP:// 手指离开屏幕


break;
}


return true;
}
});


}


public void save(View view) {
try {
File file = new File(Environment.getExternalStorageDirectory(),System.currentTimeMillis()+".jpg");
FileOutputStream stream = new FileOutputStream(file);
baseBitmap.compress(CompressFormat.JPEG, 100, stream);
stream.close();
Toast.makeText(this, "保存图片成功", 1).show();
//模拟一个消息 通知系统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 (Exception e) {
Toast.makeText(this, "保存图片失败", 1).show();
e.printStackTrace();
}



}

}

整理自 ppt和源码