android自定義組件入門實踐

定義一個小球，使其在View的Canvas中水平往返移動，當小球觸碰到右邊邊界時往左移動，小球觸碰到左邊邊界時往右移動，循環往復。

view文件：

public class BallMoveView extends View {

    private int X;
    private int Y = 100;
    private int radius = 30;
    private Paint mPaint;
    private boolean flag;//移動方向 true爲右邊，false爲左邊

    public BallMoveView(Context context, AttributeSet attrs) {
        super(context, attrs);
        //參數表示去鋸齒
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaint.setColor(Color.RED);//小球的顏色
        X = radius;
    }

    //該方法用於組件的繪圖
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        WindowManager wm = (WindowManager) getContext()
                .getSystemService(Context.WINDOW_SERVICE);
        int width = wm.getDefaultDisplay().getWidth();//獲得屏幕寬
        //int width = this.getMeasuredWidth();
        canvas.drawCircle(X, Y, radius, mPaint);
        if (X < radius) {
            flag = true;
        } else if (X > (width - radius)) {
            flag = false;
        }
        //改變x座標，當線程調用invalidate()方法後
        X = flag ? X + 5 : X - 5;//每次位移五個像素點
    }
}

佈局文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    tools:context=".MainActivity">
    
    <com.bingo.myTest.BallMoveView
        android:id="@+id/moveView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

在Activity中調用：

new Timer().schedule(new TimerTask() {
        @Override
        public void run() {
            ballMoveView.postInvalidate();
        }
    },250,50);

效果圖：