无法将正确的上下文传递给isGooglePlayServicesAvailable

Question

我的代码中有这个功能

private boolean isGoogleServiceAvailable() {
    try {
        int isAvailable = GooglePlayServicesUtil.isGooglePlayServicesAvailable(this); //ERROR
        if (isAvailable == ConnectionResult.SUCCESS) {
            return true;
        }
        else if (GooglePlayServicesUtil.isUserRecoverableError(isAvailable)) {
            Dialog dialog = GooglePlayServicesUtil.getErrorDialog(isAvailable, this, GPS_ERRORDIALOG_REQUEST);
            dialog.show();
        }
    }
    catch (Exception ex) {
        Toast.makeText(this, R.string.googleMapsServiceNotAvailable, Toast.LENGTH_LONG).show();
    }
    return false;
}

但是我在这行代码中得到java.lang.NullPointerException例外：

int isAvailable = GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);

可能是因为我没有正确传递上下文。

我的班级声明如下：

public class MapEngine extends Activity implements GooglePlayServicesClient.ConnectionCallbacks, GooglePlayServicesClient.OnConnectionFailedListener, OnItemSelectedListener {

我从我的主要活动的onCreate调用方法：

public class AppMain extends ListActivity{    
protected void onCreate(final Bundle savedInstanceState) {

            super.onCreate(savedInstanceState);
            setContentView(R.layout.main_view);

            // InitiateMap
            mapObj.isGoogleServiceAvailable();

        }

您能告诉我如何将正确的上下文传递给isGooglePlayServicesAvailable函数吗？

Answer 1

我认为这是因为您使用的是未创建的活动方法。在启动地图之前，请尝试从主应用程序检查播放服务。

public class AppMain extends ListActivity{    
protected void onCreate(final Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_view);

try {
            int isAvailable = GooglePlayServicesUtil.isGooglePlayServicesAvailable(getApplicationContext()); //ERROR
            if (isAvailable == ConnectionResult.SUCCESS) {
                return true;
            }
            else if (GooglePlayServicesUtil.isUserRecoverableError(isAvailable)) {
                Dialog dialog = GooglePlayServicesUtil.getErrorDialog(isAvailable, AppMain.this, GPS_ERRORDIALOG_REQUEST);
                dialog.show();
            }
        }
        catch (Exception ex) {
            Toast.makeText(this, R.string.googleMapsServiceNotAvailable, Toast.LENGTH_LONG).show();
        }           



    }