Android实现未读消息小红点显示实例

使用 fragmentLayout 实现，可以把小红点添加到任意 view 上。

效果 添加小红点到 textview 上

添加小红点到 imageview 上

代码实现

首先定义一个圆形 drawable

import android.graphics.Canvas;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.ShapeDrawable;

import androidx.annotation.IntRange;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

public class CircleDrawable extends ShapeDrawable {
   private Paint mPaint;
   private int mRadio;

public CircleDrawable(int radio, int painColor) {
       mPaint = new Paint();
       mPaint.setAntiAlias(true);
       mPaint.setColor(painColor);
       mRadio = radio;
   }

@Override
   public void draw(@NonNull Canvas canvas) {
       canvas.drawCircle(mRadio, mRadio, mRadio, mPaint);
   }

@Override
   public void setAlpha(@IntRange(from = 0, to = 255) int i) {
       mPaint.setAlpha(i);
   }

@Override
   public void setColorFilter(@Nullable ColorFilter colorFilter) {
       mPaint.setColorFilter(colorFilter);
   }

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

/***
    * drawable实际宽高，圆形关键
    *
    * @return
    */
   @Override
   public int getIntrinsicWidth() {
       return mRadio * 2;
   }

@Override
   public int getIntrinsicHeight() {
       return mRadio * 2;
   }
}

小红点实现

思路：
一个容器 fragmentLayout 包含两个 view （小红点view + 文本view 「当然也可以是其他的view」），通过 fragmentLayout 添加 view 重叠的特征实现

当前有待优化点：
1、通过 margin 实现小红点可以添加到任意位置「可以是有 layoutparams margin 实现」
2、其他

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Rect;
import android.graphics.drawable.ColorDrawable;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.OvalShape;
import android.graphics.drawable.shapes.RoundRectShape;
import android.util.AttributeSet;
import android.util.Printer;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.TextView;

import androidx.annotation.Nullable;

import com.primer.common.constant.GravityDirection;
import com.primer.common.mvp.LoginInterface;
import com.primer.common.util.LogHelper;
import com.primer.common.util.UiHelper;
import com.primer.common.view.drawable.CircleDrawable;

public class BadgeView extends TextView {

private final int DEFAULT_BADGE_RADIO = 5;
   private final int DEFAULT_TEXT_SIZE = 5;
   private final int DEFAULT_TEXT_COLOR = Color.WHITE;
   private final int DEFAULT_BADGE_COLOR = Color.RED;
   private final int DEFAULT_BADGE_GRAVITY = GravityDirection.DIRECT_TOP_LEFT;

private String mText;
   private int mBadgeColor = DEFAULT_BADGE_COLOR;
   private int mTextColor = DEFAULT_TEXT_COLOR;
   private int mTextSize = DEFAULT_TEXT_SIZE;
   private int mBadgeRadio = DEFAULT_BADGE_RADIO;
   private int mBadgeGravity = DEFAULT_BADGE_GRAVITY;

private FrameLayout mFragmentLayout;
   private ViewGroup mTargetViewGroup;
   private View mTarget;
   private Context mContext;

public BadgeView(Context context) {
       super(context);
       init(context);
   }

public BadgeView(Context context, @Nullable AttributeSet attrs) {
       super(context, attrs);
       init(context);
   }

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

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

private void init(Context context) {
       mFragmentLayout = new FrameLayout(context);
       mFragmentLayout.setLayoutParams(new FrameLayout.LayoutParams(
               ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
       mContext = context;
   }

/***
    *
    * @param content
    * @param target
    * @param textColor
    * @param textSize
    * @param badgeColor
    * @param badgeRadio
    */
   public void showBadgeView(String content, View target, int textColor, int textSize, int badgeColor, int badgeRadio) {
       if (target == null) {
           throw new IllegalArgumentException("target view must not be null");
       }

mTarget = target;
       mTargetViewGroup = (ViewGroup) target.getParent();
       mTargetViewGroup.removeView(target);
       mTargetViewGroup.addView(mFragmentLayout, target.getLayoutParams());

setTextColor(mTextColor);
       setTextSize(mTextSize);
       setGravity(Gravity.CENTER);
       if (content != null && content.length() <= 3) {
           setText(content);
       }

//文字和半径之间的适配
       if (content != null) {
           Rect rect = new Rect();
           this.getPaint().getTextBounds(content, 0, content.length(), rect);
           if (content.length() <= 3 && rect.width() >= mBadgeRadio) {
               mBadgeRadio = (UiHelper.px2dip(mContext, rect.width()) / 2) + 1;
           }
       }

setBackgroundDrawable(getShapeDrawable());
       mFragmentLayout.addView(target);
       mFragmentLayout.addView(this);
       mTargetViewGroup.invalidate();
   }

private ShapeDrawable getShapeDrawable() {
       int radio = UiHelper.dip2px(mContext, mBadgeRadio);
       CircleDrawable drawable = new CircleDrawable(radio, mBadgeColor);
       return drawable;
   }

/***
    *
    * @param content
    * @param target
    */
   public void showBadgeView(String content, View target) {
       showBadgeView(content, target,
               DEFAULT_TEXT_COLOR,
               DEFAULT_TEXT_SIZE,
               DEFAULT_BADGE_COLOR,
               DEFAULT_BADGE_RADIO);
   }

public void showBadgeView(View target) {
       showBadgeView(null, target,
               DEFAULT_TEXT_COLOR,
               DEFAULT_TEXT_SIZE,
               DEFAULT_BADGE_COLOR,
               DEFAULT_BADGE_RADIO);
   }

@Override
   protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
       super.onMeasure(widthMeasureSpec, heightMeasureSpec);
   }

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

@Override
   protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
       super.onLayout(changed, left, top, right, bottom);
   }
}

使用

private BadgeView mReadBadgeView;
   private TextView mRead;

mReadBadgeView = new BadgeView(getActivity());
   mReadBadgeView.showBadgeView("+99", mRead);

来源：https://blog.csdn.net/printf123scanf/article/details/122900462