安卓简单的画板

通过不断的修改BitMap来画画,需要注意的是在移动时XY坐标点需要重置.public class MainActivity extends AppCompatActivity implements View.OnClickListener {    private ImageView mImage;    /**     * 修改颜色     */    private Button mButColor;    /**     * 修改线宽     */    private Button mButLine;    private Bitmap bitmapCopy;    private Canvas canvas;    private Paint paint;    /**     * 画布Canvas  画笔paint 手势识别器     * 整体思路,因为我是图片作画,实际上是对图片进行修改,起到画图的效果     * 1.原图,白纸,画布,画笔     * 2.根据手势识别进行作画     *     * @param savedInstanceState     */    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initView();        //加载原图        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.aaa);        //做一个图片的复制        bitmapCopy = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), bitmap.getConfig());        //创建画布        canvas = new Canvas(bitmapCopy);        //创建画笔        paint = new Paint();        //开始画画        canvas.drawBitmap(bitmap,new Matrix(),paint);        //设置手势识别        mImage.setOnTouchListener(new View.OnTouchListener() {            private float starty;            private float startx;            @Override            public boolean onTouch(View view, MotionEvent motionEvent) {                switch(motionEvent.getAction()){                    case MotionEvent.ACTION_DOWN:                        startx = motionEvent.getX();                        starty = motionEvent.getY();                        break;                    case MotionEvent.ACTION_MOVE:                        float x = motionEvent.getX();                        float y = motionEvent.getY();                        canvas.drawLine(startx,starty,x,y,paint);                        startx=x;                        starty=y;                        mImage.setImageBitmap(bitmapCopy);                        break;                    default:                        break;                }                return true;            }        });    }    private void initView() {        mImage = (ImageView) findViewById(R.id.image);        mButColor = (Button) findViewById(R.id.butColor);        mButColor.setOnClickListener(this);        mButLine = (Button) findViewById(R.id.butLine);        mButLine.setOnClickListener(this);    }    //这里指示简单的修改了颜色和线宽    @Override    public void onClick(View v) {        switch (v.getId()) {            case R.id.butColor:                paint.setColor(Color.RED);                break;            case R.id.butLine:                paint.setStrokeWidth(10);//                paint.setTextSize(1500);                break;        }    }}

//保存文件

                File file=new File(path,"AA");try {        file.createNewFile();FileOutputStream fos=new FileOutputStream(file);bitmapCopy.compress(Bitmap.CompressFormat.JPEG,50,fos);} catch (IOException e) {e.printStackTrace();}