RemoteView(kotlin)

使用场景：通知栏&桌面部件

自定义通知栏

1. 通知权限申请
   manifest配置

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

权限动态申请

package com.example.kotlinlearn.Common;

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Build;
import android.os.Environment;
import android.provider.Settings;
import android.widget.Toast;

import androidx.activity.ComponentActivity;
import androidx.activity.result.ActivityResult;
import androidx.activity.result.ActivityResultCallback;
import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.core.content.ContextCompat;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

public class PermissionUtils {
    private static PermissionUtils permissionUtils;
    private String[] permissions = {
            Manifest.permission.POST_NOTIFICATIONS
    };

    private List<String> permissionList = new ArrayList<>();

    private ActivityResultLauncher<String[]> permissionLauncher;

    public static synchronized PermissionUtils getInstance() {
        if (permissionUtils == null) {
            permissionUtils = new PermissionUtils();
        }
        return permissionUtils;
    }

    private PermissionUtils() {
    }

    public void checkPermission(ComponentActivity activity) {
        permissionList.clear(); // Clear previous permission requests

        // Initialize the launcher if not already initialized
        if (permissionLauncher == null) {
            initLaunchers(activity);
        }


        for (String permission : permissions) {
            if (ContextCompat.checkSelfPermission(activity, permission) != PackageManager.PERMISSION_GRANTED) {
                permissionList.add(permission);
            }
        }
        permissionLauncher.launch(permissionList.toArray(new String[0]));

    }

    private void initLaunchers(ComponentActivity activity) {
        // Initialize the launcher for requesting permissions
        permissionLauncher = activity.registerForActivityResult(
                new ActivityResultContracts.RequestMultiplePermissions(),
                new ActivityResultCallback<Map<String, Boolean>>() {
                    @Override
                    public void onActivityResult(Map<String, Boolean> result) {
                    }
                }
        );
    }
}

2. 实现通知

package com.example.kotlinlearn.RemoteView

import android.app.NotificationChannel
import android.app.NotificationManager
import android.app.PendingIntent
import android.content.Context
import android.content.Intent
import android.graphics.Color
import android.os.Build
import android.widget.RemoteViews
import androidx.core.app.NotificationCompat
import com.example.kotlinlearn.R

object NotificationUtil {
    private const val CHANNEL_ID = "my_channel_id"
    private const val CHANNEL_NAME = "My Channel"

    fun showCustomNotification(context: Context) {
        // 创建通知渠道（仅适用于 Android O 及以上版本）
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            val channel = NotificationChannel(
                CHANNEL_ID, CHANNEL_NAME,
                NotificationManager.IMPORTANCE_DEFAULT
            ).apply {
                enableLights(true)
                lightColor = Color.RED
                enableVibration(true)
            }
            val notificationManager = context.getSystemService(NotificationManager::class.java)
            notificationManager.createNotificationChannel(channel)
        }

        // 创建 RemoteView
        val remoteViews = RemoteViews(context.packageName, R.layout.notification_layout).apply {
            setTextViewText(R.id.notification_title, "自定义通知标题")
            setTextViewText(R.id.notification_content, "这是自定义通知内容")
        }

        // 设置点击通知的行为
        val intent = Intent(context, RemoteViewActivity::class.java)
        val pendingIntent = PendingIntent.getActivity(
            context,
            0,
            intent,
            PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE
        )

        val notification = NotificationCompat.Builder(context, CHANNEL_ID)
            .setSmallIcon(R.drawable.ic_launcher_foreground)
            .setCustomContentView(remoteViews)
            .setContentIntent(pendingIntent)
            .build()

        val manager = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
        manager.notify(1, notification)
    }
}

3. activity中申请权限后直接调用就行

package com.example.kotlinlearn.RemoteView

import android.os.Bundle
import android.widget.Button
import androidx.appcompat.app.AppCompatActivity
import com.example.kotlinlearn.Common.PermissionUtils
import com.example.kotlinlearn.R


class RemoteViewActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        PermissionUtils.getInstance().checkPermission(this)
        setContentView(R.layout.activity_remote_view)
        var button = findViewById<Button>(R.id.button)
        button.setOnClickListener {
            NotificationUtil.showCustomNotification(this);
        }
    }
}

效果

自定义桌面小组件

1. 定义组件的布局样式widget_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <TextView
        android:id="@+id/widget_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello Widget"
        android:textSize="18sp" />

    <Button
        android:id="@+id/widget_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Update" />
</LinearLayout>

2. MyWidgetProvider,需要继承自AppWidgetProvider

package com.example.kotlinlearn.RemoteView

import android.app.PendingIntent
import android.appwidget.AppWidgetManager
import android.appwidget.AppWidgetProvider
import android.content.ComponentName
import android.content.Context
import android.content.Intent
import android.widget.RemoteViews
import com.example.kotlinlearn.R
import java.util.Random

class MyWidgetProvider : AppWidgetProvider() {
    override fun onUpdate(
        context: Context,
        appWidgetManager: AppWidgetManager,
        appWidgetIds: IntArray
    ) {
        for (appWidgetId in appWidgetIds) {
            val views = RemoteViews(context.packageName, R.layout.widget_layout)
            val intent = Intent(context, MyWidgetProvider::class.java)
            intent.setAction(BUTTON_CLICKED)
            val pendingIntent = PendingIntent.getBroadcast(
                context,
                0,
                intent,
                PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE
            )
            views.setOnClickPendingIntent(R.id.widget_button, pendingIntent)
            appWidgetManager.updateAppWidget(appWidgetId, views)
        }
    }

    override fun onReceive(context: Context, intent: Intent) {
        super.onReceive(context, intent)
        if (BUTTON_CLICKED == intent.action) {
            val appWidgetManager = AppWidgetManager.getInstance(context)
            val views = RemoteViews(context.packageName, R.layout.widget_layout)
            views.setTextViewText(R.id.widget_text, "Updated!" + Random().nextInt())
            val componentName = ComponentName(context, MyWidgetProvider::class.java)
            appWidgetManager.updateAppWidget(componentName, views)
        }
    }

    companion object {
        private const val BUTTON_CLICKED = "com.example.BUTTON_CLICKED"
    }
}

3. 在res/xml下创建组件的属性文件my_widget_info.xml，包括大小等值

<?xml version="1.0" encoding="utf-8"?>
<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
    android:minWidth="125dp"
    android:minHeight="50dp"
    android:updatePeriodMillis="86400000"
    android:initialLayout="@layout/widget_layout" />

4. 在manifest中配置receiver，与activity同级

        <receiver android:name=".RemoteView.MyWidgetProvider" android:exported="true">
            <intent-filter>
                <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
            </intent-filter>

            <meta-data
                android:name="android.appwidget.provider"
                android:resource="@xml/my_widget_info" />
        </receiver>

效果

点击后text会显示随机的数字。

原理

1. 可以很简单的看到，RemoteViews实现了Parcelable，所以是可序列化的，可以在进程之间传递。
   
2. 在官网可以看到，RemoteViews只支持基础的view，不支持自定义view，支持的布局以及组件如下所示
   
3. 从上面的代码示例中可以知道，在更改组件属性时使用的是setTextViewText，而不是findById。
   
   从以上的调用链可以知道，view的设置被封装在反射对象，存在mActions中，是在接收者进行真正的设置。
   可以在Action的子类中找到getMethod(view, this.methodName, param, false /* async */).invoke(view, value);，接收者正是通过反射的方式调用action中封装的view设置方法。