Android怎么实现未读消息小红点显示

今天小编给大家分享一下Android怎么实现未读消息小红点显示的相关知识点，内容详细，逻辑清晰，相信大部分人都还太了解这方面的知识，所以分享这篇文章给大家参考一下，希望大家阅读完这篇文章后有所收获，下面我们一起来了解一下吧。

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);

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