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; } @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; } 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; } 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);以上就是“Android怎么实现未读消息小红点显示”这篇文章的所有内容，感谢各位的阅读！相信大家阅读完这篇文章都有很大的收获，小编每天都会为大家更新不同的知识，如果还想学习更多的知识，请关注编程网行业资讯频道。
