经典的面试题：

a、怎样在coding过程中避免内存泄露？

b、怎样检测内存泄露？

这两个问题我想大部分 职位面试时都会被问到吧。

        怎样避免就不赘述了，网上很多答案。

       工具呢，当然也有很多，比如DDMS、MAT等，但是怎样在我们编码过程中植入内存检测代码，让我们程序在开发调试阶段就能发现内存泄露呢？好了，现在该大名鼎鼎的LeakCanary出场了，它是Square公司的一个内存探测开源项目。下面就介绍下怎样使用.

1、配置gradle依赖:    

debugCompile 'com.squareup.leakcanary:leakcanary-android:1.3.1'
releaseCompile 'com.squareup.leakcanary:leakcanary-android-no-op:1.3.1'

2、初始化Watcher

package com.micky.leakcanarysamples;;

import android.app.Application;

import com.squareup.leakcanary.LeakCanary;
import com.squareup.leakcanary.RefWatcher;

/**
 * @Project LeakCanaryTest
 * @Packate com.micky.leakcanarysamples;
 * @Description
 * @Author Micky Liu
 * @Email mickyliu@126.com
 * @Date 2016-01-04 10:32
 * @Version 1.0
 */
public class BaseApplication extends Application {

    private static BaseApplication instance;

    private RefWatcher mRefWatcher;

    @Override
    public void onCreate() {
        super.onCreate();
        instance = this;
        mRefWatcher = Constants.DEBUG ?  LeakCanary.install(this) : RefWatcher.DISABLED;
    }

    public static BaseApplication getInstance() {
        return instance;
    }

    public static RefWatcher getRefWatcher() {
        return getInstance().mRefWatcher;
    }
}

3、在Activity或Fragment中添加检测

package com.micky.leakcanarysamples;

import android.app.Activity;
import android.support.v7.app.AppCompatActivity;

/**
 * @Project LeakCanaryTest
 * @Packate com.micky.leakcanarysamples;
 * @Description
 * @Author Micky Liu
 * @Email mickyliu@126.com
 * @Date 2016-01-04 10:39
 * @Version 1.0
 */
public class BaseActivity extends AppCompatActivity {

    @Override
    protected void onDestroy() {
        super.onDestroy();
        BaseApplication.getRefWatcher().watch(this);
    }
}

4、测试

package com.micky.leakcanarysamples;;

import android.os.Bundle;
import android.os.Handler;

/**
 * @Project LeakCanaryTest
 * @Packate com.micky.leakcanarysamples;
 * @Description
 * @Author Micky Liu
 * @Email mickyliu@126.com
 * @Date 2016-01-04 10:29
 * @Version 1.0
 */
public class TestActivity extends BaseActivity {

    private final Handler mHandler = new Handler();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //模拟内存泄露
        mHandler.postDelayed(new Runnable() {
            @Override
            public void run() {

            }
        }, 3 * 60 * 1000);
        finish();
    }
}

5、测试结果

a、Toast显示（大概10秒左右显示）

b、通知显示

c、桌面自动添加的图表

d、内存泄露列表

e、内存泄露详细

LogCat可以看到日志日下（hprof文件可以用MAT打开进行分析）：

01-04 11:49:41.815 12967-13004/com.micky.leakcanarysamples I/dalvikvm: hprof: dumping heap strings to "/storage/emulated/0/Download/leakcanary/suspected_leak_heapdump.hprof".
01-04 11:49:42.020 12967-13004/com.micky.leakcanarysamples I/dalvikvm: hprof: heap dump completed (28850KB)

查看自动生成的AndroidManifest文件，LeakCanarySamples/app/build/intermediates/manifests/full/debug/AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.micky.leakcanarysamples"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="10"
        android:targetSdkVersion="23" />

    <!-- To store the heap dumps and leak analysis results. -->
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <android:uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

    <application
        android:name="com.micky.leakcanarysamples.BaseApplication"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.micky.leakcanarysamples.MainActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name="com.micky.leakcanarysamples.TestActivity" />

        <service
            android:name="com.squareup.leakcanary.internal.HeapAnalyzerService"
            android:enabled="false"
            android:process=":leakcanary" />
        <service
            android:name="com.squareup.leakcanary.DisplayLeakService"
            android:enabled="false" />

        <activity
            android:name="com.squareup.leakcanary.internal.DisplayLeakActivity"
            android:enabled="false"
            android:icon="@drawable/__leak_canary_icon"
            android:label="@string/__leak_canary_display_activity_label"
            android:taskAffinity="com.squareup.leakcanary"
            android:theme="@style/__LeakCanary.Base" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

如上所示LeakCanary给我们自动添加了两个Service和一个Activity，并添加了对SD卡的读写权限

It 's so simple.

注: 

1、如果在Release模式下请使用RefWatcher.DISABLED

 2、在Activity或Fragment 的 Destroy方法中添加检测（很好理解，就是判断一个Activity或Fragment想要被销毁的时候，是否还有其他对象持有其引用导致Activity或Fragment不能被回收，从而导致内存泄露)

源码地址:https://github.com/mickyliu945/LeakCanarySample