Question

我有一系列在onclick方法中以菊花链形式连接的AlertDialogs。在最后一个我需要发送一个URL调用并等待响应。一旦响应回来，我需要接收响应的消息并创建最后一个AlertDialog。问题是这适用于2.3 Android但由于REST http调用在UI线程上运行，因此Android 4.0的最新更改错误。所以我想把它转移到AsyncTask。我仔细阅读了教程，但没有找到我的具体困境。这是我的代码：如何使AlertDialog等待响应，同时等待显示ProgressDialog或Spinner？我正在寻找优雅的东西，其中AsyncTask是一个通用调用，并且可以在其他情况下用于REST调用。

public void onClick(View view) {

    if(alert != null && alert.isShowing()) {
        break;
    }

    alert = new AlertDialog.Builder(this)
    .setTitle(getResources().getString(R.string.alertPingTitle1).toString())
    .setMessage(getResources().getString(R.string.alertPingMessage1).toString())
    .setPositiveButton(getResources().getString(R.string.alertPingPositive1).toString(),
    new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            if (onClicked) {
                log.info("Preventing multiple clicks to Ping Node Id");
                return;
            }

            onClicked = true;
            String returnMessage = "";
            int iconId = 0;
            try {
                String url = String.format(getResources().getString(R.string.urlIdPing).toString(), getRestUrl(), getId() );

                // This is where the Rest call will happen in an AsyncTask
                AsyncRest rest = new AsyncRest( Preferences.this );
                rest.execute( new RestObject(type,null,null,true,false) );

            ..........................

                // This is the current state of the 2.3 code
                JSONObject sent = RestRequest.sendPost(RestHttp.createHttpClient(), url, null, true);
                if (sent != null && sent.getInt("response") == 200) {
                    returnMessage = "VALID REST call ";
                    iconId = android.R.drawable.ic_dialog_info;
                } else {
                    if (sent != null) {
                        returnMessage = "INVALID REST response " + "\n\n Response code: " + sent.getInt("response");
                    } else {
                        returnMessage = "INVALID REST call.";
                    }
                    iconId = android.R.drawable.ic_dialog_alert;
                }
            } catch(JSONException e) {
                returnMessage = "Errored in JSON payload.";
            }

            alert = new AlertDialog.Builder(SetPreferences.this)
            .setTitle(getResources().getString(R.string.alertPingTitle2).toString())
            .setMessage(returnMessage)
            .setIcon(iconId)
            .setPositiveButton(getResources().getString(R.string.alertOkay).toString(), 
            new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {}
            }).show();

        }
    })
}).show();

onClicked = false;

}

Answer 1

你并没有真正确定问题是什么，但我认为你不确定如何实现AsyncTask。

查看AsyncTask的开发者文档：http://developer.android.com/reference/android/os/AsyncTask.html

有一个例子，你可以在那里。基本上，您希望在AsyncTask的doInBackground()内进行REST调用。然后，在调用完成后，您需要对UI进行的任何更改都将显示在onPostExecute()。

编辑：更多细节

 private class AsyncRest extends AsyncTask<String, Void, Void> {
  protected Void doInBackground(String... url) {
     // do your REST call here
     return null;
  }

  protected void onPostExecute(Void nothing) {
     // update your UI here
  }
 }

要执行，请致电new AsyncRest().execute(url);

要获取后台任务的结果，请在执行后调用get（）。

AsyncRest rest = new AsyncRest( SetPreferences.this );
rest.execute( new RestObject(Constants.ROTypes.post,url,null,null,true,false) );
JSONObject sent = rest.get();

Answer 2

使用AsyncTask代码看起来像这样：

在你的活动中......

public MyActivity extends Activity implements AsyncRestCallback {

    public void onClick(View view) {

        if(alert != null && alert.isShowing()) {
            break;
        }

        alert = new AlertDialog.Builder(this)
        .setTitle(getResources().getString(R.string.alertPingTitle1).toString())
        .setMessage(getResources().getString(R.string.alertPingMessage1).toString())
        .setPositiveButton(getResources().getString(R.string.alertPingPositive1).toString(),
        new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                if (onClicked) {
                    log.info("Preventing multiple clicks to Ping Node Id");
                    return;
                }

                onClicked = true;
                String returnMessage = "";
                int iconId = 0;
                String url = String.format(getResources().getString(R.string.urlIdPing).toString(), getRestUrl(), getId() );

                AsyncRest rest = new AsyncRest().execute( url );
            })
    }).show();

    onClicked = false;

    }

    @Override
    public void finished(String returnMessage) {

        alert = new AlertDialog.Builder(SetPreferences.this)
        .setTitle(getResources().getString(R.string.alertPingTitle2).toString())
        .setMessage(returnMessage)
        .setIcon(iconId)
        .setPositiveButton(getResources().getString(R.string.alertOkay).toString(), 
        new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {}
        }).show();
    }
}

RestAsync

public class AsyncRest extends AsyncTask<String, Integer, String> {

    private AsyncRestCallback callback;

    public AsyncRest(AsyncRestCallback callback) {

        this.callback = callback;
    }

    @Override
    protected String doInBackground(String... params) {

        String returnMessage = "";
        String url = params[0]

        try {

            JSONObject sent = RestRequest.sendPost(RestHttp.createHttpClient(), url, null, true);
            if (sent != null && sent.getInt("response") == 200) {
                returnMessage = "VALID REST call ";
                iconId = android.R.drawable.ic_dialog_info;
            } 
            else {
                if (sent != null) {
                    returnMessage = "INVALID REST response " + "\n\n Response code: " + sent.getInt("response");
                } 
                else {
                    returnMessage = "INVALID REST call.";
                }
                iconId = android.R.drawable.ic_dialog_alert;
            }
        } catch(JSONException e) {
            returnMessage = "Errored in JSON payload.";
        }

        return returnMessage;
    }

    @Override
    protected void onPostExecute(String returnMessage) {

        callback.finished(returnMessage);
    }

    public interface AsyncRestCallback {

        public void finished(String returnMessage);
    }
}

Inner AlertDialog调用REST url，如何使用Progress Dialog等待返回

2 个答案: