Android 懸浮球的實現（如何判斷是否點擊在某View上）（如何自由拖動View）

要實現最簡單的懸浮小球需要解決兩個小問題：

1：需要判斷是否起始的觸摸屏幕在該懸浮球上面

2：自由拖動View

先解決第一個問題：

public class Point extends View {

    private Paint mPaint;

    //判斷是否再裏面
    private boolean isIn = false;

    private int lastX;
    private int lastY;


    public Point(Context context) {
        super(context, null);
    }

    public Point(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs, 0);
    }

    public Point(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        mPaint = new Paint();

        mPaint.setColor(Color.parseColor("#121212"));
        mPaint.setStyle(Paint.Style.FILL);

        mPaint.setColor(Color.parseColor("#91bef0"));
        canvas.drawCircle(0.5f * getWidth(), 0.5f * getWidth(), 0.5f * getWidth(), mPaint);



    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        int[] location = new int[2];
        this.getLocationOnScreen(location);
        int x = location[0];
        int y = location[1];
        if (event.getX() < x || event.getX() > (x + this.getWidth()) || event.getY() < y || event.getY() > (y + this.getHeight())) {
            
            return true;
        } else {
            return super.onTouchEvent(event);
        }


    }


}

主要看onTouchEvent裏面的這一段：

 int[] location = new int[2];
        this.getLocationOnScreen(location);
        int x = location[0];
        int y = location[1];
        if (event.getX() < x || event.getX() > (x + this.getWidth()) || event.getY() < y || event.getY() > (y + this.getHeight())) {

            return true;
        } else {
            return super.onTouchEvent(event);
        }

return true 上面就是點擊到該View的處理

else裏面就是默認方法。

接下來解決第二步：自由拖拽

相關的代碼就是寫在上面的true裏面

 @Override
    public boolean onTouchEvent(MotionEvent event) {

        int[] location = new int[2];
        this.getLocationOnScreen(location);
        int x = location[0];
        int y = location[1];
        if (event.getX() < x || event.getX() > (x + this.getWidth()) || event.getY() < y || event.getY() > (y + this.getHeight())) {
            //移動
            int xx = (int) event.getX();
            int yy = (int) event.getY();
            switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    lastX = xx;
                    lastY = yy;
                    break;
                case MotionEvent.ACTION_MOVE:
                    int offX = xx - lastX;
                    int offY = yy - lastY;

                    offsetLeftAndRight(offX);
                    offsetTopAndBottom(offY);

                    break;
                case MotionEvent.ACTION_UP:

                    break;
            }


            return true;
        } else {
            return super.onTouchEvent(event);
        }


    }

這個是整個onTouchEvent的方法

然後在佈局文件裏面初始化就可以了。

但是，現在要在Java代碼裏面添加的話：

public class MainActivity extends AppCompatActivity {

    private RelativeLayout mRe;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mRe = (RelativeLayout) findViewById(R.id.re);
        mRe.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                LogUtil.fussenLog().d("外面  父控件");
            }
        });


        RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(250, 250);
        params.topMargin = 250;
        params.leftMargin = 250;

        Point p = new Point(this);
        mRe.addView(p,params);


    }
}

裏面的250  代表的起始是像素點。。。

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OK完成