java - 安卓 : AlertDialog doesn't show

Question

我刚刚开始学习 Android 编程并遇到问题:我的警报对话框没有显示。

我的想法:当应用程序启动时，它会自动检查设备是否连接到互联网，并给出建议(通过警报对话框)。

我真的希望有人能找到解决方案，因为我查阅了很多教程，但每个地方都有以 onClickListener (按钮)开头的代码

代码 fragment :

public class SplashActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    checkConnection();

    Intent intent = new Intent(this, MainActivity.class);
    startActivity(intent);
    finish();
}


void checkConnection() {
    final ConnectivityManager connMgr = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);
    final android.net.NetworkInfo wifi = connMgr.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
    final android.net.NetworkInfo mobile = connMgr.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);

    AlertDialog.Builder connectionAlert = new AlertDialog.Builder(this);

    if (wifi.isConnectedOrConnecting ()) {
        // Do nothing
    } else if (mobile.isConnectedOrConnecting ()) {

        connectionAlert.setMessage("We recommend to use wifi, enable it?");
        connectionAlert.setPositiveButton("Enable", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface arg0, int arg1) {
                Toast.makeText(SplashActivity.this,"Wifi has been enabled!",Toast.LENGTH_LONG).show();
            }
        });

        connectionAlert.setNegativeButton("No",new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                finish();
            }
        });

        connectionAlert.show();

    } else {

        connectionAlert.setMessage("Please, enable internet connection!");
        connectionAlert.setNeutralButton("Wifi", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface arg0, int arg1) {
                Toast.makeText(SplashActivity.this,"Wifi has been enabled!",Toast.LENGTH_LONG).show();
            }
        });

        connectionAlert.setNeutralButton("Mobile Data", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface arg0, int arg1) {
                Toast.makeText(SplashActivity.this,"Mobile Data has been enabled!",Toast.LENGTH_LONG).show();
            }
        });

        connectionAlert.setNegativeButton("No",new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                finish();
            }
        });

        connectionAlert.show();

    }
}

}

Answer 1

添加上下文。

public class SplashActivity extends AppCompatActivity {

private Context context;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    context = this;

    checkConnection();

    Intent intent = new Intent(this, MainActivity.class);
    startActivity(intent);
    finish();
}

///////

更改此行:

AlertDialog.Builder connectionAlert = new AlertDialog.Builder(this); 

致:

AlertDialog.Builder connectionAlert = new AlertDialog.Builder(context);