android - asynctask 函数无法识别结果值
问题描述
我通过 AsyncTask 访问 JSON,但在 onPostExecute 中,字符串结果没有得到结果值。
我希望它读取 json 并返回值“perfil”,然后将新的发送到主要活动
信用谷歌翻译....
将 MainActivity 访问到 MecanismoString
String login = textousuario.getText().toString();
String senha = textosenha.getText().toString();
String urllogin = "http...."
String tipo = "";
MecanismoString mecanismoString = new MecanismoString(this, this);
mecanismoString.execute(tipo, urllogin, login, senha);
Asynctask MecanismoString
public class MecanismoString extends AsyncTask <String, String, String> {
private Interfacestring Interfacestring;
private RequestQueue requestQueue;
private StringRequest request;
private Interfacestring execinterface;
String usuario, senha, result;
Context context;
Toast toast;
public MecanismoString (Context context, Interfacestring execinterface){
this.context = context;
this.Interfacestring = execinterface;
}
@Override
public String doInBackground(String... params) {
Log.i("Script", "1 ->" + params[0]);
Log.i("Script", "2 ->" + params[1]);
Log.i("Script", "3 ->" + params[2]);
Log.i("Script", "4 ->" + params[3]);
usuario = params[2];
senha = params[3];
requestQueue = Volley.newRequestQueue(context);
request = new StringRequest(Request.Method.POST, params[1], new Response.Listener<String>() {
@Override
public void onResponse(String response) {
try {
JSONObject jsonObject = new JSONObject(response);
result = jsonObject.getString("perfil");
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
}){
@Override
protected Map<String, String> getParams() throws AuthFailureError {
HashMap<String, String> hashMap = new HashMap<String, String>();
hashMap.put("login", usuario);
hashMap.put("senha", senha);
return hashMap;
}
};
requestQueue.add(request);
return (result);
}
@Override
protected void onPostExecute(String result) {
execinterface.carregarString(result);
}
}
返回 MecanismoString 值的代码
public void carregarString(String result) {
Toast.makeText(context.getApplicationContext(),
result,
Toast.LENGTH_SHORT) .show();
}
错误日志
E/AndroidRuntime: FATAL EXCEPTION: main
Process: ic.eng.br.eunaobra, PID: 13735
java.lang.NullPointerException: Attempt to invoke interface method 'void ic.eng.br.eunaobra.Interfacestring.carregarString(java.lang.String)' on a null object reference
at ic.eng.br.eunaobra.MecanismoString.onPostExecute(MecanismoString.java:94)
at ic.eng.br.eunaobra.MecanismoString.onPostExecute(MecanismoString.java:22)
at android.os.AsyncTask.finish(AsyncTask.java:695)
at android.os.AsyncTask.-wrap1(Unknown Source:0)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:712)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6944)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
I/System.out: (HTTPLog)-Static: isSBSettingEnabled false
(HTTPLog)-Static: isSBSettingEnabled false
I/qtaguid: Untagging socket 76 failed errno=-22
W/NetworkManagementSocketTagger: untagSocket(76) failed with errno -22
Application terminated.
解决方案
请传递正确的上下文和 execinterface 对象:
MecanismoString mecanismoString = new MecanismoString(MainActivity.this, correct execinterface object);
请删除getApplicationContext()
,carregarString()
因为您已经有context
:
public void carregarString(String result) {
Toast.makeText(context,result,Toast.LENGTH_SHORT) .show();
}
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