Android - 自定义视图，无法正确绘制

Question

我有点卡住了。

我尝试创建一个像表格一样的自定义视图！但是 onDraw 方法只是绘制第一个单元格/矩形。

这是我的看法：

public class CustomView extends View {


    private static int ROWS = 8;
    private static int COLS = 8;

    final Paint p = new Paint();

    public CustomView(Context context) {
        super(context);

        p.setColor(Color.GREEN);
    }

    @Override
    public void onDraw(Canvas canvas) {
        canvas.drawColor(Color.RED);

        float width = getWidth();
        float height = getHeight();
        float cellWidth = width/COLS;
        float cellHeight = height/ROWS;

        for(float row = 0; row<ROWS; row++) {
            for(float col = 0; col<COLS; col++) {
                RectF cell = new RectF( (cellWidth*col), (cellHeight*row), cellWidth, cellHeight);
                canvas.drawRect(cell, p);
            }
        }
    }

}

我的 XML：

<?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:id="@+id/mainLayout"
    android:orientation="vertical"
    android:background="#000000"
    tools:context="com.biegertfunk.qlocktwo.Act_Main">


    <RelativeLayout
        android:id="@+id/centerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

我的活动：

public class Act_Main extends AppCompatActivity {


//views
public CustomView mainView;


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

    int size = getSize();

    RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(size, size);
    layoutParams.addRule(RelativeLayout.CENTER_IN_PARENT);


    RelativeLayout mainLayout = (RelativeLayout) findViewById(R.id.centerView);

    mainView = new CustomView(this);

    mainLayout.addView(mainView, layoutParams);

}

private int getSize() {
    Display display = getWindowManager().getDefaultDisplay();
    Point size = new Point();
    display.getSize(size);
    int width = size.x;
    int height = size.y;

    if(width>height) {
        return height;
    } else {
        return width;
    }
}

}

但结果只显示一个矩形：

Answer 1

您在onDraw() 中计算的cell 是错误的。试试这个方法：

RectF cell = new RectF( 
    (cellWidth*col), (cellHeight*row), 
    (cellWidth*col)+cellWidth, (cellHeight*row)+cellHeight
);

RectF的构造函数是

RectF(float left, float top, float right, float bottom)

不是

RectF(float left, float top, float width, float height) // WRONG

请参阅文档here。

Answer 2

RectF 方法中传递的参数顺序不正确。正如您在RectF documentation 中此方法的文档中看到的那样 您将看到参数的顺序分别为left、top、right 和bottom。此外，您的左参数必须小于或等于右参数，这可能不会在您的代码中看到。

Answer 3

添加代码

invalidate();

到

for(float row = 0; row<ROWS; row++) {
        for(float col = 0; col<COLS; col++) {
            RectF cell = new RectF( (cellWidth*col), (cellHeight*row), cellWidth, cellHeight);
            canvas.drawRect(cell, p);
            invalidate();
        }
    }