Android 实现简单画板二

一、首先自定义一个画板控件

/**
 * @描述 画板view
 * @项目名称 App_Basic
 * @包名 com.example.basic.canvas
 * @类名 CanvasView
 * @author chenlin
 * @date 2013年5月17日 下午9:57:25
 * @version 1.0
 */

public class CanvasView extends View {
    //private static final int VIEW_WIDTH = 320;
    //private static final int VIEW_HEIGHT = 480;

    //控件的宽高
    private int mWidth;
    private int mHeight;

    private Path mPath;//路径
    public Paint mPaint;//画笔
    private Bitmap mCacheBitmap;//缓存图片
    private Canvas mCanvas;//画布

    public CanvasView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    public CanvasView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public CanvasView(Context context) {
        super(context);
        init();
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        mWidth = w;
        mHeight = h;
        super.onSizeChanged(w, h, oldw, oldh);
    }

    private void init() {
        mCanvas = new Canvas();
        mPath = new Path();
        mPaint = new Paint(Paint.DITHER_FLAG);
        mPaint.setColor(Color.RED);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeWidth(2);
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
    }

    private float preX;
    private float preY;
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        float x = event.getX();  
        float y = event.getY();  

        switch (event.getAction()) {  
        case MotionEvent.ACTION_DOWN:  
            mPath.moveTo(x, y);  
            preX = x;  
            preY = y;  
            break;  
        case MotionEvent.ACTION_MOVE:  
            mPath.quadTo(preX, preY, x, y);  
            preX = x;  
            preY = y;  
            break;  
        case MotionEvent.ACTION_UP:  
            mCanvas.drawPath(mPath, mPaint);  
            //mPath.reset();  
            break;  
        }  
        invalidate();  
        return true;  
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        mCacheBitmap = Bitmap.createBitmap(mWidth, mHeight, Config.ARGB_8888);
        mCanvas.setBitmap(mCacheBitmap);
        canvas.drawBitmap(mCacheBitmap, 0, 0, null);  
        canvas.drawPath(mPath, mPaint);  
    }

}

二、创建Activity实现

/**
 * @描述 画板
 * @项目名称 App_Basic
 * @包名 com.example.basic.canvas
 * @类名 CanvasActivity
 * @author chenlin
 * @date 2013年5月17日 下午10:17:13
 * @version 1.0
 */

public class CanvasActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // 设置为无标题
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        // 设置为全屏模式
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
        super.onCreate(savedInstanceState);
        CanvasView view = new CanvasView(this);
        LayoutParams layoutParams = new ViewGroup.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
        view.setLayoutParams(layoutParams);
        setContentView(view);
    }
}