以编程方式创建 "Circle Button" 未绘制

Question

我有一个习惯CircleButtonclass:

public class CircleButton extends ImageView {

private  int radius;
private  int x;
private  int y;

public CircleButton(Context context) {
    super(context);
    constructorTask();
}

public CircleButton(Context context, AttributeSet attrs) {
    super(context, attrs);
    constructorTask();
}

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

public CircleButton(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
    super(context, attrs, defStyleAttr, defStyleRes);
    constructorTask();
}


private void constructorTask() {
    x = 300;
    y = 300;
    radius = 100;
}

@Override
public void setPressed(boolean pressed) {
    super.setPressed(pressed);
    Log.i("Button Logger","Button Pressed");
}

@Override
protected  void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.drawCircle(x, y, radius, GameView.green);
    Log.i("Drawing status", "CircleButton Drawing...");
}

}

我有一个 activity。此 activity 包含具有单个自定义视图的相对布局。

这是自定义视图：

public class GameView extends View {

public static Paint green = new Paint();

public GameView(Context context) {
    super(context);
    green.setARGB(255,0,255,0);
}

public GameView(Context context, AttributeSet attrs) {
    super(context, attrs);
    green.setARGB(255, 0, 255, 0);

}

public GameView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    green.setARGB(255, 0, 255, 0);
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    Log.i("GameView Draw Status","Drawing...");
    Main.testButton.invalidate();
    invalidate();
}

}

这里是 activity 代码：

public class Main extends AppCompatActivity {

public static CircleButton testButton;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    testButton = new CircleButton(getApplicationContext());
    makeFullScreen();

        RelativeLayout screenLayout = (RelativeLayout) findViewById(R.id.screenLayout);
    screenLayout.addView(testButton);
}

private void makeFullScreen() {...}

 }

出于某种原因，我的 testButton 没有被绘制。为什么画不出来？

编辑一：这是我的 XML。

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:paddingBottom="0dp"
    android:paddingLeft="0dp"
    android:paddingRight="0dp"
    android:paddingTop="0dp"
    tools:context="com.example.vroy.customcirclebuttontest.Main"
    android:id="@+id/screenLayout">

    <com.example.vroy.customcirclebuttontest.GameView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/black"
        android:id="@+id/gameScreen" />


</RelativeLayout>

编辑二：我通过向相关布局添加一个普通按钮进行了一些进一步的调试，它工作正常。

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        testCircleButton = new CircleButton(getApplicationContext());
        makeFullScreen();

        testButton = new Button(getApplicationContext());
        testButton.setX(100);
        testButton.setY(100);
        testButton.setText("HELLO WORLD");

        RelativeLayout screenLayout = (RelativeLayout) findViewById(R.id.screenLayout);
        screenLayout.addView(testCircleButton);
        screenLayout.addView(testButton);

        Log.i("Button Status","Adding Button To Layout");
    }

出于某种原因，circleButton 无法正常工作，但普通按钮可以。

Answer 1

您没有指定视图的大小（layout_width 和 layout_height），因此您的视图在 0px x 0px space 内呈现，因此不可见。在将视图添加到布局之前，您可以使用 LayoutParams 以编程方式设置它们。

例如绝对尺寸：

testButton.setLayoutParams(new ViewGroup.LayoutParams(100,100));

不过请记住 px 和 dip 之间的区别。您可能希望使用内部半径属性而不是对它们进行硬编码来设置值。

以编程方式创建 "Circle Button" 未绘制

Programmatically created "Circle Button" not drawing

android

android-custom-view

android-button