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WebView存在的内存泄漏
## 0. Notice - earlier version
* 要使用WebView不造成内存泄漏，首先应该做的就是不能在xml中定义webview节点，而是在需要的时候动态生成。即：可以在使用WebView的地方放置一个LinearLayout类似ViewGroup的节点，然后在要使用WebView的时候，动态生成即：
```java
WebView mWebView = new WebView(getApplicationgContext());
LinearLayout mll = findViewById(R.id.xxx);
mll.addView(mWebView);
```
然后一定要在onDestroy()方法中显式的调用:
```java
protected void onDestroy() {
super.onDestroy();
mWebView.removeAllViews();
mWebView.destroy()
}
```
注意： new WebView(getApplicationgContext()) ;必须传入ApplicationContext如果传入Activity的Context的话，对内存的引用会一直被保持着。有人用这个方法解决了当Activity被消除后依然保持引用的问题。但是你会发现，如果你需要在WebView中打开链接或者你打开的页面带有flash，获得你的WebView想弹出一个dialog，都会导致从ApplicationContext到ActivityContext的强制类型转换错误，从而导致你应用崩溃。
## 1. What leads to Memory leak
### 1.1 InnerClass
```java
public class InnerClassActivity extends Activity{
private static Leak mLeak;
class Leak {
int a = 3;
private Context mLeakContext;
Leak(Context context) {
mLeakContext = context;
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.test);
mLeak = new Leak(this);
Toast.makeText(this, "This is InnerClassActivity", Toast.LENGTH_SHORT).show();
}
}
```
### 1.2 Singleton
```java
public class Singleton {
private static Singleton instance;
private Context mContext1;
private Singleton(Context context) {
this.mContext1 = context;
}
public static Singleton getInstance(Context context) {
if(instance == null) {
synchronized (Singleton.class) {
if (instance == null) {
instance = new Singleton(context);
}
}
}
return instance;
}
}
```
### 1.3 webview - earlier version
```java
public class WebViewCreateActivity extends Activity{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.webview_create);
LinearLayout ll = (LinearLayout) findViewById(R.id.ll);
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
WebView webView = new WebView(this);
webView.setLayoutParams(layoutParams);
WebSettings webSettings = webView.getSettings();
webSettings.setJavaScriptEnabled(true);
webSettings.setDomStorageEnabled(true);
webView.loadUrl("https://www.baidu.com/");
ll.addView(webView);
Toast.makeText(this, "Hello", Toast.LENGTH_SHORT).show();
}
}
```
## 2. How to detect the Memory Leak
### 2.1 Android Studio
* GC manually
* dump Java Heap
### 2.2 MemoryLeak in Our Project
| 品牌 | 固件 | 泄漏点 |
| --- | ---- | -------- |
| 三星 | 4.0.4 | LightAppManager
| 小米 | 5.0.1 | LightAppManager/ mAccessibilityManager
| 华为 | 6.0 | LightAppManager/ mAccessibilityManager
#### 2.2.1 LightAppManager泄漏
3次手动GC后，内存的增长：
泄漏点1： LightAppManager 泄漏
泄漏点2： WebView-wrapper getSystemService泄漏
## 3. 官方态度
` It‘s 2016 now and, as far as I can see it, the issue still hasn‘t been resolved. I tested it on Nexus 5 and Nexus 6 with the latest WebView updates (since the component is now separate from the OS itself). Could someone, please, take a look at this issue?! `来源： https://code.google.com/p/android/issues/detail?id=9375
WebView存在的内存泄漏
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