android {
  defaultConfig {
    renderscriptTargetApi 21
    renderscriptSupportModeEnabled true
  }
}

// ==============================================
// 文件：BlurDemoActivity.java
// 功能：演示動態(tài)高斯模糊背景的使用
// 包含：布局 XML，Gradle 配置，BlurView 控件源碼
// ==============================================
 
package com.example.blurviewdemo;
 
import android.graphics.Bitmap;
import android.os.Build;
import android.os.Bundle;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
 
/*
=========================== app/build.gradle ===========================
android {
  compileSdk 33
  defaultConfig {
    applicationId "com.example.blurviewdemo"
    minSdk 21
    targetSdk 33
    // 啟用 RenderScript 兼容模式
    renderscriptTargetApi 21
    renderscriptSupportModeEnabled true
  }
  // ...
}
dependencies {
  implementation 'androidx.appcompat:appcompat:1.5.1'
  implementation 'com.google.code.gson:gson:2.9.0' // 如需 JSON 解析
}
=========================== Gradle 結束 ===========================
*/
 
/*
=========================== res/layout/activity_main.xml ===========================
<?xml version="1.0" encoding="utf-8"?>
<!-- 父布局：背景內容 -->
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/rootContainer"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <!-- 1. 背景內容示例 -->
    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="centerCrop"
        android:src="@drawable/your_large_image"/>
    <!-- 2. 動態(tài)模糊遮罩層 -->
    <com.example.blurviewdemo.BlurView
        android:id="@+id/blurView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:blurRadius="16"
        app:downsampleFactor="4"
        app:updateInterval="100"/>
    <!-- 3. 前端 UI 元素 -->
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="動態(tài)高斯模糊示例"
        android:textSize="24sp"
        android:textColor="#FFFFFFFF"
        android:layout_gravity="center"/>
</FrameLayout>
=========================== 布局結束 ===========================
*/
 
public class BlurDemoActivity extends AppCompatActivity {
    @Override protected void onCreate(@Nullable Bundle s) {
        super.onCreate(s);
        setContentView(R.layout.activity_main);
        // 無需額外代碼，BlurView 會在 attached 時自動工作
    }
}
 
// ==============================================
// 文件：BlurView.java
// 功能：通用的動態(tài)高斯模糊遮罩控件
// ==============================================
 
package com.example.blurviewdemo;
 
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.*;
import android.os.Build;
import android.renderscript.*;
import android.util.AttributeSet;
import android.view.*;
import android.widget.FrameLayout;
 
import androidx.annotation.Nullable;
 
public class BlurView extends FrameLayout {
 
    private int blurRadius;         // 模糊半徑
    private int downsampleFactor;   // 降采樣倍數(shù)
    private long updateInterval;    // 更新間隔 ms
 
    private Bitmap bitmapBuffer;
    private Canvas  bitmapCanvas;
    private Paint   paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private boolean useRenderEffect;
    private RenderScript rs;
    private ScriptIntrinsicBlur instBlur;
    private Allocation allocIn, allocOut;
 
    private ViewTreeObserver.OnPreDrawListener preDrawListener;
    private long lastUpdateTime = 0;
 
    public BlurView(Context c) { this(c, null); }
    public BlurView(Context c, AttributeSet attrs) { this(c, attrs, 0); }
    public BlurView(Context c, AttributeSet attrs, int defStyle) {
        super(c, attrs, defStyle);
        // 讀取屬性
        TypedArray a = c.obtainStyledAttributes(attrs, R.styleable.BlurView);
        blurRadius       = a.getInt(R.styleable.BlurView_blurRadius, 10);
        downsampleFactor = a.getInt(R.styleable.BlurView_downsampleFactor, 4);
        updateInterval   = a.getInt(R.styleable.BlurView_updateInterval, 100);
        a.recycle();
 
        // 決定使用哪種模糊方式
        useRenderEffect = Build.VERSION.SDK_INT >= Build.VERSION_CODES.S;
 
        if (!useRenderEffect) {
            // 初始化 RenderScript 模糊
            rs = RenderScript.create(c);
            instBlur = ScriptIntrinsicBlur.create(rs, Element.U8_4(rs));
            instBlur.setRadius(blurRadius);
        }
 
        setWillNotDraw(false); // 允許 onDraw
    }
 
    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        // 注冊 PreDraw 監(jiān)聽
        preDrawListener = () -> {
            long now = System.currentTimeMillis();
            if (now - lastUpdateTime >= updateInterval) {
                lastUpdateTime = now;
                blurAndInvalidate();
            }
            return true;
        };
        getViewTreeObserver().addOnPreDrawListener(preDrawListener);
    }
 
    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        // 清理
        getViewTreeObserver().removeOnPreDrawListener(preDrawListener);
        if (rs != null) rs.destroy();
    }
 
    /** 執(zhí)行模糊并重繪自己 */
    private void blurAndInvalidate() {
        // 獲取父容器快照
        View root = (View) getParent();
        if (root == null) return;
 
        int width  = root.getWidth();
        int height = root.getHeight();
        if (width == 0 || height == 0) return;
 
        int bw = width  / downsampleFactor;
        int bh = height / downsampleFactor;
 
        // 初始化緩存
        if (bitmapBuffer == null ||
            bitmapBuffer.getWidth()!=bw ||
            bitmapBuffer.getHeight()!=bh) {
            bitmapBuffer = Bitmap.createBitmap(bw, bh, Bitmap.Config.ARGB_8888);
            bitmapCanvas = new Canvas(bitmapBuffer);
        }
        // 將 root 縮放繪制到 bitmap
        bitmapCanvas.save();
        bitmapCanvas.scale(1f/downsampleFactor, 1f/downsampleFactor);
        root.draw(bitmapCanvas);
        bitmapCanvas.restore();
 
        // 模糊
        if (useRenderEffect) {
            // API 31+: 直接在自己上設置 RenderEffect
            RenderEffect effect = RenderEffect.createBlurEffect(
                blurRadius, blurRadius, Shader.TileMode.CLAMP);
            setRenderEffect(effect);
        } else {
            // RenderScript 模糊
            if (allocIn!=null) allocIn.destroy();
            if (allocOut!=null) allocOut.destroy();
            allocIn  = Allocation.createFromBitmap(rs, bitmapBuffer);
            allocOut = Allocation.createTyped(rs, allocIn.getType());
            instBlur.setInput(allocIn);
            instBlur.forEach(allocOut);
            allocOut.copyTo(bitmapBuffer);
            // 將模糊結果拷貝到自己的 bitmap
            invalidate();
        }
    }
 
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (!useRenderEffect && bitmapBuffer!=null) {
            // 繪制放大回屏幕
            canvas.save();
            canvas.scale(downsampleFactor, downsampleFactor);
            canvas.drawBitmap(bitmapBuffer, 0, 0, paint);
            canvas.restore();
        }
    }
}
 
// ==============================================
// res/values/attrs.xml（整合在此）
// ==============================================
/*
<resources>
  <declare-styleable name="BlurView">
    <attr name="blurRadius" format="integer"/>
    <attr name="downsampleFactor" format="integer"/>
    <attr name="updateInterval" format="integer"/>
  </declare-styleable>
</resources>
*/