安卓TelephonyManager权限

Question

我正在尝试编码一个快速的应用程序，给我所需的3G值，当我点击一个按钮。但是首先我需要检查一下我是否连接到了3G网络。但是，我的权限有一些问题。我有以下代码：

public void calculate(View view) {
    TextView rscp = (TextView) findViewById(R.id.RSCP);
    TextView rssi = (TextView) findViewById(R.id.RSSI);
    TextView ecno = (TextView) findViewById(R.id.EcNo);
    TelephonyManager tm = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
    if (Arrays.stream(values_3G).anyMatch(n -> n == tm.getDataNetworkType())) {
        for (CellInfo cellInfo : tm.getAllCellInfo()) {
            if (cellInfo instanceof CellInfoWcdma) {
                CellSignalStrengthWcdma cellSignalStrength = ((CellInfoWcdma) cellInfo).getCellSignalStrength();
                rscp.setText(cellSignalStrength.getDbm());
                ecno.setText(cellSignalStrength.getEcNo());
                int rssiValue = -113 + 2 * cellSignalStrength.getAsuLevel();
                rssi.setText(rssiValue);
            }
        }
    } else {
        rscp.setText(0);
        rssi.setText(0);
        ecno.setText(0);
        Log.i(TAG, "No 3G Mobile connection detected!");
        Toast.makeText(getApplicationContext(), "Connect to 3G", Toast.LENGTH_SHORT).show();

    }

}

关于READ_PHONE_STATE，tm.getDataNetworkType()给了我以下问题：

Call requires permission which may be rejected by user: code should explicitly check to see if permission is available (with checkPermission) or explicitly handle a potential SecurityException

如果我在Android Studio中按照说明检查权限，得到的结果如下：

if (ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_PHONE_STATE) != PackageManager.PERMISSION_GRANTED) {
        // TODO: Consider calling
        //    ActivityCompat#requestPermissions
        // here to request the missing permissions, and then overriding
        //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
        //                                          int[] grantResults)
        // to handle the case where the user grants the permission. See the documentation
        // for ActivityCompat#requestPermissions for more details.
        return;
    }

我需要在括号之间填写什么？

Answer 1

创建权限请求代码的全局最终int

final int PHONE_REQUEST_CODE = 101;

如果未授予权限，则请求权限

if (ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_PHONE_STATE) != PackageManager.PERMISSION_GRANTED) {

    requestPermissions(new String[]{Manifest.permission.READ_PHONE_STATE},
                       PHONE_REQUEST_CODE); // triggers onRequestPermissionsResult()

} else {
     // calculate(myView); // Do whatever you want as the permission is already granted
}

并在活动中重写onRequestPermissionsResult()

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    if (grantResults.length == 0)
        return;

    if (requestCode == PHONE_REQUEST_CODE) {
        if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
           // calculate(myView); // Do whatever you want after the permission is granted
}

并在manifest.xml中添加权限。

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