Question

我正在尝试获取细胞信号强度，只是在文本视图中显示它。我相信CellSignalStrength.getLevel（）返回一个INT，但是当我运行此代码时，我收到以下错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'int android.telephony.CellSignalStrength.getLevel()' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
            at android.app.ActivityThread.-wrap11(ActivityThread.java)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:148)
            at android.app.ActivityThread.main(ActivityThread.java:5417)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.telephony.CellSignalStrength.getLevel()' on a null object reference
            at com.steel.signaltest.MainActivity.onCreate(MainActivity.java:22)
            at android.app.Activity.performCreate(Activity.java:6251)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
            at android.app.ActivityThread.-wrap11(ActivityThread.java)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:148)
            at android.app.ActivityThread.main(ActivityThread.java:5417)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

这是我的代码：

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.telephony.CellSignalStrength;
import android.telephony.TelephonyManager;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
import android.telephony.CellSignalStrength;





public class MainActivity extends AppCompatActivity {

    public CellSignalStrength signal;
    public int strength;
    public TextView view;





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





        strength = signal.getLevel();

        view = (TextView) findViewById(R.id.view);
        view.setText(strength);





    }

Answer 1

CellSignalStrength为空。

以下是一个例子：

TelephonyManager telephonyManager = (TelephonyManager)this.getSystemService(Context.TELEPHONY_SERVICE);
// for example value of first element
CellInfoGsm cellinfogsm = (CellInfoGsm)telephonyManager.getAllCellInfo().get(0);
CellSignalStrengthGsm cellSignalStrengthGsm = cellinfogsm.getCellSignalStrength();
cellSignalStrengthGsm.getDbm();

Android中的CellSignalStrength类，并获得作为INT的强度级别

1 个答案: