这是我的第一个 Activity
public class MainActivity extends SampleActivityBase {
private boolean mLogShown;
public static final String TAG = "MainActivity";
private SharedPreferences pref;
EditText cardnumber;
TextView foodorders;
Button buttonorder, addsub;
private static final int REQUEST_CODE = 10;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
pref = getPreferences(0);
setContentView(R.layout.activity_main);
cardnumber = (EditText) findViewById(R.id.card_account_field);
cardnumber.setText(AccountStorage.GetAccount(getBaseContext()));
cardnumber.addTextChangedListener(new AccountUpdater());
foodorders = (TextView) findViewById(R.id.foodordershow);
buttonorder = (Button) findViewById(R.id.buttonorder);
addsub = (Button) findViewById(R.id.buttonregister);
addsub.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Intent intent = new Intent(getApplicationContext(), MainActivity1.class);
startActivity(intent);
}
});
buttonorder.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String strcardnumber = cardnumber.getText().toString();
Intent intent = new Intent(getApplicationContext(), activityresult1.class);
intent.putExtra("Card Number", strcardnumber);
startActivityForResult(intent, REQUEST_CODE);
}
});
}
private class AccountUpdater implements TextWatcher {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
// Not implemented.
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
// Not implemented.
}
@Override
public void afterTextChanged(Editable s) {
String account = s.toString();
AccountStorage.SetAccount(getBaseContext(), account);
}
}
这是我的第二个 Activity
public class MainActivity1 extends AppCompatActivity {
private SharedPreferences pref;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main1);
pref = getPreferences(0);
initFragment();
}
private void initFragment(){
Fragment fragment;
if(pref.getBoolean(Constants.IS_LOGGED_IN,false)){
fragment = new ProfileFragment();
}else {
fragment = new LoginFragment();
}
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.fragment_frame,fragment);
ft.commit();
}
个人资料 fragment
public class ProfileFragment extends Fragment implements View.OnClickListener {
private TextView tv_name,tv_email,tv_message;
private SharedPreferences pref;
private AppCompatButton btn_change_password,btn_logout;
private EditText et_old_password,et_new_password;
private AlertDialog dialog;
private ProgressBar progress;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_profile,container);
initViews(view);
return view;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
pref = getActivity().getPreferences(0);
tv_name.setText("Welcome : "+pref.getString(Constants.NAME,""));
tv_email.setText(pref.getString(Constants.EMAIL,""));
}
private void initViews(View view){
tv_name = (TextView)view.findViewById(R.id.tv_name);
tv_email = (TextView)view.findViewById(R.id.tv_email);
btn_change_password = (AppCompatButton)view.findViewById(R.id.btn_chg_password);
btn_logout = (AppCompatButton)view.findViewById(R.id.btn_logout);
btn_change_password.setOnClickListener(this);
btn_logout.setOnClickListener(this);
}
private void showDialog(){
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
LayoutInflater inflater = getActivity().getLayoutInflater();
View view = inflater.inflate(R.layout.dialog_change_password, null);
et_old_password = (EditText)view.findViewById(R.id.et_old_password);
et_new_password = (EditText)view.findViewById(R.id.et_new_password);
tv_message = (TextView)view.findViewById(R.id.tv_message);
progress = (ProgressBar)view.findViewById(R.id.progress);
builder.setView(view);
builder.setTitle("Change Password");
builder.setPositiveButton("Change Password", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
dialog = builder.create();
dialog.show();
dialog.getButton(AlertDialog.BUTTON_POSITIVE).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String old_password = et_old_password.getText().toString();
String new_password = et_new_password.getText().toString();
if(!old_password.isEmpty() && !new_password.isEmpty()){
progress.setVisibility(View.VISIBLE);
changePasswordProcess(pref.getString(Constants.EMAIL,""),old_password,new_password);
}else {
tv_message.setVisibility(View.VISIBLE);
tv_message.setText("Fields are empty");
}
}
});
}
@Override
public void onClick(View v) {
switch (v.getId()){
case R.id.btn_chg_password:
showDialog();
break;
case R.id.btn_logout:
logout();
break;
}
}
private void logout() {
SharedPreferences.Editor editor = pref.edit();
editor.putBoolean(Constants.IS_LOGGED_IN,false);
editor.putString(Constants.EMAIL,"");
editor.putString(Constants.NAME,"");
editor.putString(Constants.UNIQUE_ID,"");
editor.apply();
goToLogin();
}
private void goToLogin(){
Fragment login = new LoginFragment();
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.fragment_frame,login);
ft.commit();
}
private void changePasswordProcess(String email,String old_password,String new_password){
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(Constants.BASE_URL)
.addConverterFactory(GsonConverterFactory.create())
.build();
com.example.android.cardemulation.RequestInterface requestInterface = retrofit.create(com.example.android.cardemulation.RequestInterface.class);
User user = new User();
user.setEmail(email);
user.setOld_password(old_password);
user.setNew_password(new_password);
ServerRequest request = new ServerRequest();
request.setOperation(Constants.CHANGE_PASSWORD_OPERATION);
request.setUser(user);
Call<ServerResponse> response = requestInterface.operation(request);
response.enqueue(new Callback<ServerResponse>() {
@Override
public void onResponse(Call<ServerResponse> call, retrofit2.Response<ServerResponse> response) {
ServerResponse resp = response.body();
if(resp.getResult().equals(Constants.SUCCESS)){
progress.setVisibility(View.GONE);
tv_message.setVisibility(View.GONE);
dialog.dismiss();
Snackbar.make(getView(), resp.getMessage(), Snackbar.LENGTH_LONG).show();
}else {
progress.setVisibility(View.GONE);
tv_message.setVisibility(View.VISIBLE);
tv_message.setText(resp.getMessage());
}
}
@Override
public void onFailure(Call<ServerResponse> call, Throwable t) {
Log.d(Constants.TAG,"failed");
progress.setVisibility(View.GONE);
tv_message.setVisibility(View.VISIBLE);
tv_message.setText(t.getLocalizedMessage());
}
});
}
登录 fragment
公共(public)类 LoginFragment 扩展 Fragment 实现 View.OnClickListener{
private AppCompatButton btn_login;
private EditText et_email,et_password;
private TextView tv_register;
private ProgressBar progress;
private SharedPreferences pref;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_login,container,false);
initViews(view);
return view;
}
private void initViews(View view){
pref = getActivity().getPreferences(0);
btn_login = (AppCompatButton)view.findViewById(R.id.btn_login);
tv_register = (TextView)view.findViewById(R.id.tv_register);
et_email = (EditText)view.findViewById(R.id.et_email);
et_password = (EditText)view.findViewById(R.id.et_password);
progress = (ProgressBar)view.findViewById(R.id.progress);
btn_login.setOnClickListener(this);
tv_register.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch (v.getId()){
case R.id.tv_register:
goToRegister();
break;
case R.id.btn_login:
String email = et_email.getText().toString();
String password = et_password.getText().toString();
if(!email.isEmpty() && !password.isEmpty()) {
progress.setVisibility(View.VISIBLE);
loginProcess(email,password);
} else {
Snackbar.make(getView(), "Fields are empty !", Snackbar.LENGTH_LONG).show();
}
break;
}
}
private void loginProcess(String email,String password){
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(Constants.BASE_URL)
.addConverterFactory(GsonConverterFactory.create())
.build();
com.example.android.cardemulation.RequestInterface requestInterface = retrofit.create(com.example.android.cardemulation.RequestInterface.class);
User user = new User();
user.setEmail(email);
user.setPassword(password);
ServerRequest request = new ServerRequest();
request.setOperation(Constants.LOGIN_OPERATION);
request.setUser(user);
Call<ServerResponse> response = requestInterface.operation(request);
response.enqueue(new Callback<ServerResponse>() {
@Override
public void onResponse(Call<ServerResponse> call, retrofit2.Response<ServerResponse> response) {
ServerResponse resp = response.body();
Snackbar.make(getView(), resp.getMessage(), Snackbar.LENGTH_LONG).show();
if(resp.getResult().equals(Constants.SUCCESS)){
SharedPreferences.Editor editor = pref.edit();
editor.putBoolean(Constants.IS_LOGGED_IN,true);
editor.putString(Constants.EMAIL,resp.getUser().getEmail());
editor.putString(Constants.NAME,resp.getUser().getName());
editor.putString(Constants.UNIQUE_ID,resp.getUser().getUnique_id());
editor.apply();
goToProfile();
}
progress.setVisibility(View.INVISIBLE);
}
@Override
public void onFailure(Call<ServerResponse> call, Throwable t) {
progress.setVisibility(View.INVISIBLE);
Log.d(Constants.TAG,"failed");
Snackbar.make(getView(), t.getLocalizedMessage(), Snackbar.LENGTH_LONG).show();
}
});
}
private void goToRegister(){
Fragment register = new com.example.android.cardemulation.RegisterFragment();
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.fragment_frame,register);
ft.commit();
}
private void goToProfile(){
Fragment profile = new com.example.android.cardemulation.ProfileFragment();
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.fragment_frame,profile);
ft.commit();
}
当我按下按钮 register addsub 时，它崩溃了，并弹出此消息:
04-22 14:35:04.384 10045-10045/com.example.android E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.android, PID: 10045
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android/com.example.android.cardemulation.MainActivity1}: java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first. at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2484) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2544) at android.app.ActivityThread.access$900(ActivityThread.java:150) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1394) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:168) at android.app.ActivityThread.main(ActivityThread.java:5845) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:797) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:687) Caused by: java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first. at android.view.ViewGroup.addViewInner(ViewGroup.java:4315) at android.view.ViewGroup.addView(ViewGroup.java:4151) at android.view.ViewGroup.addView(ViewGroup.java:4092) at android.view.ViewGroup.addView(ViewGroup.java:4065) at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:985) at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1148) at android.app.BackStackRecord.run(BackStackRecord.java:793) at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1535) at android.app.FragmentController.execPendingActions(FragmentController.java:325) at android.app.Activity.performStart(Activity.java:6263) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2447) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2544) at android.app.ActivityThread.access$900(ActivityThread.java:150) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1394) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:168) at android.app.ActivityThread.main(ActivityThread.java:5845) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:797) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:687)
最佳答案
不要在您的 Intent 中使用 getApplicationContext()。使用“本地”上下文
Intent intent = new Intent(MainActivity.this, MainActivity1.class);
//or
Intent intent = new Intent(v.getContext(), MainActivity1.class);
//or, define a global variable in your Activity, outside the onClick:
Context context;
//in onCreate:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
pref = getPreferences(0);
setContentView(R.layout.activity_main);
context = this;
//your other code...
// in onClick:
addsub.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Intent intent = new Intent(context, MainActivity1.class);
startActivity(intent);
}
});
编辑:
您的 ProfilFragment 中的 onCreateView 似乎缺少一个参数。
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_profile,container, false); //<--- Added false!
initViews(view);
return view;
}
标准是将 View 附加到父 View ，因此您需要告诉充气器不要附加它。
关于java - 无法从 Activity 到 Activity，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/36786652/