'com.example.volleyexample.app.AppController' 不可分配给 'android.app.Activity'

Question

不知道为什么会出现这个错误

遗漏的地方添加一些代码或删除代码。

我会尝试 JSon 对象请求

我要 2 class AppController AND LruBitmapCache

Manifest.xml 的屏幕截图：

activity_main.xml :

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</LinearLayout>

下面的代码是 AppController.java class:

package com.example.volleyexample.app;

import android.app.Application;
import android.text.TextUtils;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.ImageLoader;
import com.android.volley.toolbox.Volley;
import com.example.volleyexample.utils.LruBitmapCache;

public class AppController extends Application{

    public static final String TAG = AppController.class.getSimpleName();

    private RequestQueue mRequestQueue;
    private ImageLoader mImageLoader;
    private static AppController mInstance;

    @Override
    public void onCreate() {
        super.onCreate();
        mInstance = this;
    }

    public static synchronized AppController getInstance() {
        return mInstance;
    }

    public RequestQueue getRequestQueue() {
        if (mRequestQueue == null) {
            mRequestQueue = Volley.newRequestQueue(getApplicationContext());
        }

        return mRequestQueue;
    }

    public ImageLoader getImageLoader() {
        getRequestQueue();
        if (mImageLoader == null) {
            mImageLoader = new ImageLoader(this.mRequestQueue,
                    new LruBitmapCache());
        }
        return this.mImageLoader;
    }

    public <T> void addToRequestQueue(Request<T> req, String tag) {
        // set the default tag if tag is empty
        req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
        getRequestQueue().add(req);
    }

    public <T> void addToRequestQueue(Request<T> req) {
        req.setTag(TAG);
        getRequestQueue().add(req);
    }

    public void cancelPendingRequests(Object tag) {
        if (mRequestQueue != null) {
            mRequestQueue.cancelAll(tag);
        }
    }
}

提前致谢:)

Answer 1

您必须使用 Activity 名称 添加正确的包名称。

android:name

The name of the class that implements the activity, a subclass of Activity. The attribute value should be a fully qualified class name (such as, "com.example.project.ExtracurricularActivity"). However, as a shorthand, if the first character of the name is a period (for example, ".ExtracurricularActivity"), it is appended to the package name specified in the element.

您应该添加 正确的包名称 Activity 名称 。

<activity android:name="yourPackageName.ActivityName

android:parentActivity姓名

The class name of the logical parent of the activity. The name here must match the class name given to the corresponding element's android:name attribute.

注意

你的AppController是Applicationclass，所以应该是<application部分.

终于

<application
        android:name="com.example.volleyexample.app.AppController"
        android:allowBackup="true"
       >
        <activity
            android:name="
        >

然后Clean-Rebuild-Run.

Answer 2

应该在manifest的Application标签中。如下所示

<application
        android:name=".yourPackage.AppController"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

// Your activities, services... declared here

</application>

'com.example.volleyexample.app.AppController' 不可分配给 'android.app.Activity'

'com.example.volleyexample.app.AppController' is not assignable to 'android.app.Activity'

xml

android

android-manifest