为什么我的广播接收器没有响应任何电话状态？

Question

Actually, I want a broadcast receiver that can read the phone state like calling , OFFHOOK , idle . here is my code.

I have added the <uses-permission> for reading Phone State in Manifest file

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

Here is my Statically registered Receiver

<receiver android:name=".CallStateBroadcast">
        <intent-filter>
            <action android:name="android.intent.action.PHONE_STATE"/>
        </intent-filter>
</receiver>

This is the MainActivity.Java

package com.example.callstateapp;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {
    CallStateBroadcast myReceiver = new CallStateBroadcast();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(TelephonyManager.EXTRA_STATE);
        registerReceiver(myReceiver,intentFilter);
    }
}

This is CallStateBroadcast.Class

package com.example.callstateapp;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.telephony.TelephonyManager;
import android.widget.Toast;

public class CallStateBroadcast extends BroadcastReceiver {
    Context mContext;
    @Override
    public void onReceive(final Context context, Intent intent)
    {
        String state = intent.getStringExtra(TelephonyManager.EXTRA_STATE);

        if (state.equals(TelephonyManager.EXTRA_STATE_RINGING))
            Toast.makeText(context, "Ringing...", Toast.LENGTH_SHORT).show();
        if (state.equals(TelephonyManager.EXTRA_STATE_OFFHOOK))
            Toast.makeText(context, "Busy...", Toast.LENGTH_SHORT).show();
        if (state.equals(TelephonyManager.EXTRA_STATE_IDLE))
            Toast.makeText(context, "Free...", Toast.LENGTH_SHORT).show();
    }
}

Answer 1

You need to register your receiver class at least once when your application starts. You can add this in your MainActivity.java file and it will work.

MainActivity.java

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    CallStateBroadcast myReceiver = new CallStateBroadcast();
    IntentFilter intentFilter = new IntentFilter();
    intentFilter.addAction(TelephonyManager.EXTRA_STATE);
    registerReceiver(myReceiver,intentFilter);
}

CallStateBroadcast.java

public class CallStateBroadcast extends BroadcastReceiver {
    Context mContext;
    @Override
    public void onReceive(final Context context, Intent intent)
    {
        String state = intent.getStringExtra(TelephonyManager.EXTRA_STATE);

        if (state.equals(TelephonyManager.EXTRA_STATE_RINGING)) {
            Log.e("Zed", "ringing");
            Toast.makeText(context, "Ringing...", Toast.LENGTH_SHORT).show();
        }
        if (state.equals(TelephonyManager.EXTRA_STATE_OFFHOOK)) {
            Log.e("Zed", "offhook");
            Toast.makeText(context, "Busy...", Toast.LENGTH_SHORT).show();
        }
        if (state.equals(TelephonyManager.EXTRA_STATE_IDLE)) {
            Log.e("Zed", "idle");
            Toast.makeText(context, "Free...", Toast.LENGTH_SHORT).show();
        }
    }
}

AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.myapplication">

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

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

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

    <receiver android:name=".CallStateBroadcast">
        <intent-filter>
            <action android:name="android.intent.action.PHONE_STATE"/>
        </intent-filter>
    </receiver>
</application>

Edit

I uploaded my sample project code for you to check. MinSdk version 21, TargetSdk 30.

Here is the recording of working. https://i.stack.imgur.com/wqqqO.gif

Answer 2

To use READ_PHONE_STATE you need:

Note: If both your minSdkVersion and targetSdkVersion values are set to 3 or lower, the system implicitly grants your app this permission. If you don't need this permission, be sure your targetSdkVersion is 4 or higher.

Then, you need to specify:

<uses-sdk
 android:minSdkVersion="20"
 android:targetSdkVersion="whatyouwant" />