創建透明

我嘗試創建這樣的繪製創建透明

我寫的代碼，幾乎正常工作

public class GetsugaDrawable extends Drawable { 

private final Context context; 
private final float radiusScale = 1.2f; 
private final float yOffset = 0.3f; 

private final int colorLower = Color.RED; 
private final int colorUpper = Color.BLACK; 

private final Paint upperPaint = new Paint(); 

public GetsugaDrawable(Context c) { 
    context = c; 
    upperPaint.setColor(colorUpper); 
    upperPaint.setFlags(Paint.ANTI_ALIAS_FLAG); 
} 

@Override 
public void draw(@NonNull Canvas canvas) { 
    final Rect bounds = new Rect(getBounds()); 
    canvas.drawColor(colorLower, PorterDuff.Mode.SRC); 
    final float radius = radiusScale * bounds.height(); 
    final int x = bounds.centerX(); 
    final float y = (bounds.centerY() - bounds.height() * yOffset) - radius; 
    canvas.drawCircle(x, y, radius, upperPaint); 
} 

@Override 
public void setAlpha(int alpha) { 
    // ignored TODO impl. 
} 

@Override 
public void setColorFilter(@Nullable ColorFilter colorFilter) { 
    // ignored TODO impl. 
} 

@Override 
public int getOpacity() { 
    return PixelFormat.TRANSLUCENT; 
} 
}

這裏半圈背景繪製的是我的結果

我試圖改變

private final int colorUpper = Color.BLACK;

與

private final int colorUpper = Color.TRANSPARENT;

但是當我透明色再次運行我的應用程序，結果是這樣的

我在做什麼錯？謝謝

來源

2017-09-22 BekaKK

正確的解決方法是使用形狀，不拉絲手動：https://developer.android.com/guide/topics/resources/drawable-resource.html#Shape –

在你的代碼的問題，那你繪製透明圈在紅色背景。當然，沒有什麼會改變。您應該繪製像素並且不要繪製透明區域。 –

你在哪裏使用這個GetsugaDrawable？ – Ankita

添加upperPaint.setXfermode（new PorterDuffXfermode（PorterDuff.Mode.CLEAR））;

public class GetsugaDrawable extends Drawable { 
private final Context context; 
private final float radiusScale = 1.2f; 
private final float yOffset = 0.3f; 

private final int colorLower = Color.RED; 
private final int colorUpper = Color.BLACK; 

private final Paint upperPaint = new Paint(); 

public GetsugaDrawable(Context c) { 
    context = c; 
    upperPaint.setAntiAlias(true); 
    upperPaint.setColor(colorUpper); 
    upperPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));  
} 

@Override 
public void draw(@NonNull Canvas canvas) { 
    final Rect bounds = new Rect(getBounds()); 
    canvas.drawColor(colorLower); 
    final float radius = radiusScale * bounds.height(); 
    final int x = bounds.centerX(); 
    final float y = (bounds.centerY() - bounds.height() * yOffset) - radius; 
    canvas.drawCircle(x, y, radius, upperPaint); 
} 

@Override 
public void setAlpha(int alpha) { 

} 

@Override 
public void setColorFilter(@Nullable ColorFilter colorFilter) { 

} 

@Override 
public int getOpacity() { 
    return PixelFormat.TRANSLUCENT; 
}}

而且不要忘了view.setLayerType（View.LAYER_TYPE_HARDWARE，NULL）;在目標視圖上

來源

2017-09-22 08:35:55

您可以更改draw函數。

@Override 
public void draw(@NonNull Canvas canvas) { 
    final Rect bounds = new Rect(getBounds()); 
    final float radius = radiusScale * bounds.height(); 
    final int x = bounds.centerX(); 
    final float y = (bounds.centerY() - bounds.height() * yOffset) - radius; 
    Path path = new Path(); 
    path.addCircle(x, y, radius, CW); 
    canvas.clipPath(path, Region.Op.DIFFERENCE); 
    canvas.drawColor(colorLower); 
}

試試這個。

來源

2017-09-22 08:59:02 amuyu

回答

相關問題