Question

我正在尝试创建一个与Web服务器api连接的登录应用程序。当我在android studio中构建文件时，一切都很顺利。但是在模拟器/真实Android设备中运行应用程序后，当我单击登录按钮时，应用程序已停止。

MainActivity在这里：

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

TextInputLayout username, password;
Button button;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    TextView myTextView = (TextView) findViewById(R.id.textView5);
    Typeface typeface=Typeface.createFromAsset(getAssets(), "fonts/solaimanlipi.ttf");
    myTextView.setTypeface(typeface);
    initializtion();

}

private void initializtion() {
    final TextInputLayout username = (TextInputLayout) findViewById(R.id.username);
    final TextInputLayout password = (TextInputLayout) findViewById(R.id.password);
    username.setHint("Username");
    password.setHint("Password");
    button = (Button) findViewById(R.id.button);
    button.setOnClickListener(this);
}

@Override
public void onClick(View view) {
    int id = view.getId();
    if(id == R.id.button){
        if (!CommonTask.isOnline(this)) {
            CommonTask.goSettingPage(this);
            return;
        }
        validation_check();
    }
}

private void validation_check() {
    if(username.getEditText().getText().toString().trim().equals("")){
        username.setError("Please enter user name");
        return;
    }
    if(password.getEditText().getText().toString().trim().equals("")){
        password.setError("Please enter your password");
        return;
    }
    doLogin();
}

private void doLogin() {

    try{

        String url=String.format(CommonURL.getInstance().login,username.getEditText().getText().toString().trim(),
                password.getEditText().getText().toString().trim());
        final ProgressDialog progressDialog = new ProgressDialog(this);
        progressDialog.setMessage("Login , Please wait");
        progressDialog.setCancelable(false);
        progressDialog.show();

        JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, url, "",
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject obj) {
                        progressDialog.dismiss();
                        if(obj != null){
                            LoginResponse response = new Gson().fromJson(obj.toString(), LoginResponse.class);
                            if(response.result.equals("valid")){

                                CommonTask.savePreferences(getApplicationContext(), CommonContents.USERNAME,username.getEditText().getText().toString().trim());
                                CommonTask.savePreferences(getApplicationContext(), CommonContents.PASSWORD,password.getEditText().getText().toString().trim());
                                CommonTask.savePreferences(getApplicationContext(), CommonContents.isLoggedIn,"1");
                                // Toast.makeText(getApplicationContext(), "Login Succesfull", Toast.LENGTH_SHORT).show();
                                Intent intent=new Intent(getApplicationContext(),HomePage.class);
                                startActivity(intent);
                                finish();
                            }else{
                                Toast.makeText(getApplicationContext(), "Wrong UserID or Password.", Toast.LENGTH_SHORT).show();
                            }
                        }
                    }
                }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                progressDialog.dismiss();
                Toast.makeText(getApplicationContext(), "Unexpected error.", Toast.LENGTH_SHORT).show();
            }
        });

        request.setRetryPolicy(new DefaultRetryPolicy(30000, DefaultRetryPolicy.DEFAULT_MAX_RETRIES, DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
        MainApp.getInstance().addToRequestQueue(request, "Login");
    }catch (Exception ex){
        CommonTask.showLog(ex.getMessage());
    }
}
}

但是当我点击按钮时，Android Studio会给我这个logcat：

E/AndroidRuntime: FATAL EXCEPTION: main
              java.lang.NullPointerException
                  at com.mateors.mastererp.activity.MainActivity.validation_check(MainActivity.java:68)
                  at com.mateors.mastererp.activity.MainActivity.onClick(MainActivity.java:63)
                  at android.view.View.performClick(View.java:4084)
                  at android.view.View$PerformClick.run(View.java:16966)
                  at android.os.Handler.handleCallback(Handler.java:615)
                  at android.os.Handler.dispatchMessage(Handler.java:92)
                  at android.os.Looper.loop(Looper.java:137)
                  at android.app.ActivityThread.main(ActivityThread.java:4745)
                  at java.lang.reflect.Method.invokeNative(Native Method)
                  at java.lang.reflect.Method.invoke(Method.java:511)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
                  at dalvik.system.NativeStart.main(Native Method)

Answer 1

在initialization功能中，您不必再次声明username和password字段。这里应该使用全局变量。您在代码中声明了两个局部变量，这些变量是错误的，并且无法在此范围之外找到。

这是修改后的initialization功能。

private void initializtion() {
    username = (TextInputLayout) findViewById(R.id.username);
    password = (TextInputLayout) findViewById(R.id.password);
    username.setHint("Username");
    password.setHint("Password");
    button = (Button) findViewById(R.id.button);
    button.setOnClickListener(this);
}

现在在validation_check函数中，您需要从这些EditText获取文本。

private void validation_check() {
    if(username.getText().toString().trim().equals("")){
        username.setError("Please enter user name");
        return;
    }

    if(password.getText().toString().trim().equals("")){
        password.setError("Please enter your password");
        return;
    }

    doLogin();
}

这样做。

登录Web服务器api JSON按钮单击无法正常工作

1 个答案: