使用canvas画图

package com.example.paintcustomcontrol;

import android.annotation.SuppressLint;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

private ImageView image;
Bitmap bitmap;
Bitmap bmcopy;
Canvas canvas;
private Button button1;
private Button button2;
private Button button3;
private Button button4;
int startX;
int startY;
int stopX;
int stopY;
 Paint paint;
@SuppressLint("ClickableViewAccessibility")
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate( savedInstanceState );
    setContentView( R.layout.activity_main );
    initView();
    //加载原图

/* bitmap = BitmapFactory.decodeResource( getResources(), R.drawable.a );

    //创建白纸,设置宽高图片等参数
    bmcopy = Bitmap.createBitmap( bitmap.getWidth(), bitmap.getHeight(), bitmap.getConfig() );

    //创建画板
    canvas = new Canvas( bmcopy );

    //创建画笔
    paint = new Paint();

    paint.setStrokeWidth( 5 );

    //在纸上画画,白纸在画板
    canvas.drawBitmap( bitmap, new Matrix(), paint );*/
    bitmap = BitmapFactory.decodeResource( getResources(), R.drawable.a );
    bmcopy = Bitmap.createBitmap( this.bitmap.getWidth(), this.bitmap.getHeight(), this.bitmap.getConfig() );
    canvas = new Canvas( bmcopy );
    paint = new Paint();

    canvas.drawBitmap( bitmap,new Matrix(),paint );

    image.setOnTouchListener( new View.OnTouchListener() {
        @Override
        public boolean onTouch(View view, MotionEvent motionEvent) {

//
switch (motionEvent.getAction()) {

                case MotionEvent.ACTION_DOWN:
                    startX = (int) motionEvent.getX();
                    startY = (int) motionEvent.getY();

                 //   canvas.drawLine( startX,startY,stopX,stopY,paint);

                 //   image.setImageBitmap(bmcopy);
                    //  int x = (int) motionEvent.getX();
                    //  int y = (int) motionEvent.getY();
                    //   Log.e( "text","X坐标"+x+"   "+"Y坐标"+y);
                    //     Log.e( "text","+"+y+"+");


                    break;
                case MotionEvent.ACTION_MOVE:
                    stopX = (int) motionEvent.getX();
                    stopY = (int) motionEvent.getY();

                    canvas.drawLine( startX,startY,stopX,stopY, MainActivity.this.paint );
                    startX=stopX;
                    startY=stopY;

                    image.setImageBitmap(bmcopy);

// int x = (int) motionEvent.getX();
// int y = (int) motionEvent.getY();
// Log.e( “text”, “X坐标” + x + " " + “Y坐标” + y );
break;

                case MotionEvent.ACTION_UP:

                    break;
            }
            return true;
        }
    } );
}

private void initView() {
    image = (ImageView) findViewById( R.id.image );
    button1 = (Button) findViewById( R.id.button1 );
    button1.setOnClickListener( this );
    button2 = (Button) findViewById( R.id.button2 );
    button2.setOnClickListener( this );
    button3 = (Button) findViewById( R.id.button3 );
    button3.setOnClickListener( this );
    button4 = (Button) findViewById( R.id.button4 );
    button4.setOnClickListener( this );
}

@Override
public void onClick(View v) {
    switch (v.getId()) {
        case R.id.button1:
            paint.setColor( Color.RED );
            break;
        case R.id.button2:
            paint.setColor( Color.BLACK);
            break;
        case R.id.button3:
            if(bmcopy!=null){
                canvas.drawColor( Color.GRAY );
                image.setImageBitmap( bmcopy );
            }
            break;
        case R.id.button4:

try {
// 保存图片到SD卡上
File file = new File( Environment.getExternalStorageDirectory(),
System.currentTimeMillis() + “.png”);
FileOutputStream stream = new FileOutputStream(file);
bmcopy.compress(Bitmap.CompressFormat.PNG, 100, stream);
Toast.makeText(MainActivity.this, “保存图片成功”, Toast.LENGTH_LONG).show();

                // Android设备Gallery应用只会在启动的时候扫描系统文件夹
                // 这里模拟一个媒体装载的广播,用于使保存的图片可以在Gallery中查看
                Intent intent = new Intent();
                intent.setAction(Intent.ACTION_MEDIA_MOUNTED);
                intent.setData( Uri.fromFile(Environment
                        .getExternalStorageDirectory()));
                sendBroadcast(intent);
            } catch (Exception e) {
                Toast.makeText(MainActivity.this, "保存图片失败", Toast.LENGTH_LONG).show();
                e.printStackTrace();
            }
            break;
    }
}

}

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