Android AsyncTask内存泄漏警告：AsyncTaskUploadClass如何用弱引用修复

问题根因 #

你当前定义的AsyncTaskUploadClass是方法内的非静态内部类，默认会持有外部UploadActivity的强引用。如果上传任务未执行完成时Activity就被销毁，这个强引用会导致Activity无法被垃圾回收器回收，从而引发内存泄漏，这就是系统弹出警告的原因。

解决方案 #

核心思路是将AsyncTask改为静态内部类，通过弱引用持有Activity实例，同时通过构造方法传入所有需要的参数，避免直接引用外部类的变量：

1. 首先将AsyncTask从方法内移出，改为Activity的静态内部类，添加弱引用持有逻辑，通过构造方法接收所需参数

// 定义为Activity的静态内部类
private static class AsyncTaskUploadClass extends AsyncTask<Void,Void,String> {
    // 弱引用持有Activity，避免强引用导致内存泄漏
    private final WeakReference<UploadActivity> activityWeakReference;
    private final String imageName;
    private final String userName;
    private final String imageBase64;
    private ProgressDialog progressDialog;

    // 构造方法传入所有需要用到的参数
    public AsyncTaskUploadClass(UploadActivity activity, String imageName, String userName, String imageBase64) {
        this.activityWeakReference = new WeakReference<>(activity);
        this.imageName = imageName;
        this.userName = userName;
        this.imageBase64 = imageBase64;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        UploadActivity activity = activityWeakReference.get();
        // 操作UI前先判断Activity是否存活，不存活直接取消任务
        if (activity == null || activity.isFinishing() || activity.isDestroyed()) {
            cancel(true);
            return;
        }
        progressDialog = ProgressDialog.show(activity,"数据正在上传中....",false,false);
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        UploadActivity activity = activityWeakReference.get();
        if (activity == null || activity.isFinishing() || activity.isDestroyed()) {
            return;
        }
        if (progressDialog != null && progressDialog.isShowing()) {
            progressDialog.dismiss();
        }
        // 如需处理上传结果，可调用activity的公共方法处理
        // activity.handleUploadResult(result);
    }

    @Override
    protected String doInBackground(Void... params) {
        if (isCancelled()) {
            return null;
        }
        ImageProcessClass imageProcessClass = new ImageProcessClass();
        HashMap<String,String> HashMapParams = new HashMap<>();
        HashMapParams.put(ImageName1, imageName);
        HashMapParams.put(UserName, userName);
        HashMapParams.put(ImagePath1, imageBase64);
        return imageProcessClass.ImageHttpRequest(ServerUploadPath, HashMapParams);
    }
}

2. 调整原来的触发方法逻辑

public void ImageUploadToServerFunction(){
    String imageName1 = GetImageNameEditText1.trim();
    String userName = GetUserName.trim();
    String imageView1 = getStringImage1(bitmap1);
    AsyncTaskUploadClass uploadTask = new AsyncTaskUploadClass(this, imageName1, userName, imageView1);
    uploadTask.execute();
    // 建议将uploadTask存为Activity的成员变量，方便后续取消任务
    // mCurrentUploadTask = uploadTask;
}

额外优化建议 #

• 重写Activity的onDestroy生命周期方法，调用mCurrentUploadTask.cancel(true)取消未完成的上传任务，避免资源浪费
• 所有涉及UI操作的逻辑都要先校验弱引用获取到的Activity是否存活，避免空指针异常

内容的提问来源于stack exchange，提问作者shinsky Paul