Question

如果未启用GPS，我将使用以下方法将用户带到设置页面。但它抛出异常 null。

public void showSettingsAlert() {
    try {
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

        alertDialog.setTitle("GPS Settings");

        alertDialog.setMessage("Please enable GPS. Do you want to go to settings menu?");

        // On pressing Settings button
        alertDialog.setPositiveButton("Settings",
            new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                    Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                    mContext.startActivity(intent);
                }
            }
        );

        // on pressing cancel button
        alertDialog.setNegativeButton("Cancel",
            new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                    dialog.cancel();
                }
            }
        );

        // Showing Alert Message
        alertDialog.show();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

有人可以帮助我。

Answer 1

使用以下行

AlertDialog alertDialog = alertDialogBuilder.create();

将此行添加到您的代码

public void showSettingsAlert() {
    try {
        AlertDialog.Builder alertDialogBuilder= new AlertDialog.Builder(mContext);

        alertDialogBuilder.setTitle("GPS Settings");

        alertDialogBuilder
                .setMessage("Please enable GPS. Do you want to go to settings menu?");

        // On pressing Settings button
        alertDialogBuilder.setPositiveButton("Settings",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        Intent intent = new Intent(
                                Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                        mContext.startActivity(intent);
                    }
                });

        // on pressing cancel button
        alertDialog.setNegativeButton("Cancel",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.cancel();
                    }
                });

//added this line
     AlertDialog alertDialog = alertDialogBuilder.create();

        // Showing Alert Message
        alertDialog.show();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

Answer 2

我认为你没有初始化变量 mContext 所以用当前的Activity初始化它，如 mContext = this;

Answer 3

我找到了解决方案。关于这个问题的R＆amp; D表明从服务中调用AlertDialog不是一个好习惯。所以我正在创建一个主题为@android的新活动：style / Theme.DeviceDefault.Dialog作为Service的系统覆盖窗口，并点击该布局的OK按钮调用设置页面，代码如下。

    Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
    this.startActivity(intent);
    this.finish();

我正在从我的其他服务中调用此活动。

            Intent intent;
            intent = new Intent(this,
                    SettingsAlertActivity.class);
            intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            this.startActivity(intent);

使用AlertDialog将用户带到设置页面时出现空例外

3 个答案: