我想通知用户有关应用程序中新的未读消息，该消息可通过抽屉导航访问。我正在考虑通知徽章类似于Apple的东西，但在工具栏中的抽屉切换。

这就是我现在拥有的:

这就是我想要的:

我怎样才能做到这一点？

最佳答案

我在互联网上发现了这个非常酷的 BadgeDrawable 类，您可以使用该类将徽章计数添加到任何可绘制对象。请按照以下步骤操作。

第 1 步:首先将以下类添加到您的项目中。

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.Rect;
import android.graphics.Typeface;
import android.graphics.drawable.Drawable;
import android.util.TypedValue;


/**
 * Created by Admin on 2/25/2016.
 */
public class BadgeDrawable extends Drawable {

    private float mTextSize;
    private Paint mBadgePaint;
    private Paint mBadgePaint1;
    private Paint mTextPaint;
    private Rect mTxtRect = new Rect();

    private String mCount = "";
    private boolean mWillDraw = false;


    public BadgeDrawable(Context context) {
        mTextSize = dpToPx(context, 8); //text size
        mBadgePaint = new Paint();
        mBadgePaint.setColor(Color.RED);
        mBadgePaint.setAntiAlias(true);
        mBadgePaint.setStyle(Paint.Style.FILL);
        mBadgePaint1 = new Paint();
        mBadgePaint1.setColor(Color.parseColor("#EEEEEE"));
        mBadgePaint1.setAntiAlias(true);
        mBadgePaint1.setStyle(Paint.Style.FILL);

        mTextPaint = new Paint();
        mTextPaint.setColor(Color.WHITE);
        mTextPaint.setTypeface(Typeface.DEFAULT);
        mTextPaint.setTextSize(mTextSize);
        mTextPaint.setAntiAlias(true);
        mTextPaint.setTextAlign(Paint.Align.CENTER);
    }

    private float dpToPx(Context context, float value) {
        Resources r = context.getResources();
        float px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, value, r.getDisplayMetrics());
        return px;
    }


    @Override
    public void draw(Canvas canvas) {
        if (!mWillDraw) {
            return;
        }
        Rect bounds = getBounds();
        float width = bounds.right - bounds.left;
        float height = bounds.bottom - bounds.top;
        // Position the badge in the top-right quadrant of the icon.

  /*Using Math.max rather than Math.min */
//        float radius = ((Math.max(width, height) / 2)) / 2;
        float radius = width * 0.15f;
        float centerX = (width - radius - 1) +10;
        float centerY = radius -5;
        if(mCount.length() <= 2){
            // Draw badge circle.
            canvas.drawCircle(centerX, centerY, radius+9, mBadgePaint1);
            canvas.drawCircle(centerX, centerY, radius+7, mBadgePaint);
        }
        else{
            canvas.drawCircle(centerX, centerY, radius+10, mBadgePaint1);
            canvas.drawCircle(centerX, centerY, radius+8, mBadgePaint);
        }
        // Draw badge count text inside the circle.
        mTextPaint.getTextBounds(mCount, 0, mCount.length(), mTxtRect);
        float textHeight = mTxtRect.bottom - mTxtRect.top;
        float textY = centerY + (textHeight / 2f);
        if(mCount.length() > 2)
        canvas.drawText("99+", centerX, textY, mTextPaint);
        else
        canvas.drawText(mCount, centerX, textY, mTextPaint);
    }

    /*
     Sets the count (i.e notifications) to display.
      */
    public void setCount(String count) {
        mCount = count;
        // Only draw a badge if there are notifications.
        mWillDraw = !count.equalsIgnoreCase("0");
        invalidateSelf();
    }

    @Override
    public void setAlpha(int alpha) {
        // do nothing
    }

    @Override
    public void setColorFilter(ColorFilter cf) {
        // do nothing
    }

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

第 2 步:现在创建一个可绘制对象(在我的例子中是 ic_badge_drawable.xml)。然后复制并粘贴到xml文本下方。

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:id="@+id/ic_main_icon"
        android:drawable="@drawable/ic_burger"
        android:gravity="center" />


    <!-- set a place holder Drawable so android:drawable isn't null -->
    <item android:id="@+id/ic_badge"
        android:drawable="@drawable/ic_burger" />
</layer-list>

这里你现在可以传递任何drawable，以后我们可以传递任何drawable给那些。这些就像占位符一样。

第 3 步:我们已经完成了所有设置。现在您可以使用以下方法为任何可绘制对象设置徽章计数。

 private Drawable setBadgeCount(Context context, int res, int badgeCount){
        LayerDrawable icon = (LayerDrawable) ContextCompat.getDrawable(context, R.drawable.ic_badge_drawable);
        Drawable mainIcon = ContextCompat.getDrawable(context, res);
        BadgeDrawable badge = new BadgeDrawable(context);
        badge.setCount(String.valueOf(badgeCount));
        icon.mutate();
        icon.setDrawableByLayerId(R.id.ic_badge, badge);
        icon.setDrawableByLayerId(R.id.ic_main_icon, mainIcon);

        return icon;
    }

第 4 步:我使用它来更改我的默认汉堡图标。

setSupportActionBar(toolbar);
getSupportActionBar().setHomeAsUpIndicator(setBadgeCount(this,R.drawable.ic_burger, 3));
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowCustomEnabled(true);   // enable overriding the default toolbar layout
getSupportActionBar().setDisplayShowTitleEnabled(false);// disable the default title element here (for centered title)

关于android - 工具栏中抽屉切换的徽章通知 - Android，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33200741/