Make password-setting AsyncTask survive configuration changes (screen rotation)

Robust code derived from:
http://stackoverflow.com/a/12303649

res/layout/activity_set_password.xml

@@ -1,62 +1,26 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
-    android:layout_height="match_parent"
-    android:padding="10dp"
-    android:orientation="vertical" >
+    android:layout_height="match_parent" >
 
-    <TextView
-        android:layout_width="wrap_content"
-        android:layout_height="wrap_content"
-        android:text="@string/old_password"
-        android:textAppearance="?android:attr/textAppearanceMedium" />
-
-    <EditText
-        android:id="@+id/password_old"
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
-        android:ems="10"
-        android:inputType="textPassword" >
+        android:orientation="vertical" >
 
-        <requestFocus />
-    </EditText>
+        <fragment
+            android:id="@+id/set_password_frag"
+            android:name="i2p.bote.SetPasswordFragment"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            tools:layout="@layout/fragment_set_password" >
+        </fragment>
 
-    <TextView
-        android:layout_width="wrap_content"
-        android:layout_height="wrap_content"
-        android:text="@string/new_password"
-        android:textAppearance="?android:attr/textAppearanceMedium" />
+        <FrameLayout
+            android:id="@+id/password_waiter_frag"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content" />
+    </LinearLayout>
 
-    <EditText
-        android:id="@+id/password_new"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:ems="10"
-        android:inputType="textPassword" />
-
-    <TextView
-        android:layout_width="wrap_content"
-        android:layout_height="wrap_content"
-        android:text="@string/confirm_new_password"
-        android:textAppearance="?android:attr/textAppearanceMedium" />
-
-    <EditText
-        android:id="@+id/password_confirm"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:ems="10"
-        android:inputType="textPassword" />
-
-    <Button
-        android:id="@+id/submit_password"
-        android:layout_width="wrap_content"
-        android:layout_height="wrap_content"
-        android:text="OK" />
-
-    <TextView
-        android:id="@+id/error"
-        android:layout_width="wrap_content"
-        android:layout_height="wrap_content"
-        android:textColor="@color/error_color" />
-
-</LinearLayout>
+</ScrollView>

res/layout/dialog_status.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical"
+    android:padding="10dp" >
+
+    <TextView
+        android:id="@+id/status"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content" />
+
+    <ProgressBar
+        style="?android:attr/progressBarStyleHorizontal"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:indeterminateOnly="true" />
+
+</LinearLayout>

res/layout/fragment_set_password.xml

@@ -0,0 +1,70 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical"
+    android:paddingLeft="10dp"
+    android:paddingRight="10dp"
+    android:paddingTop="10dp" >
+
+    <TextView
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="@string/old_password"
+        android:textAppearance="?android:attr/textAppearanceMedium" />
+
+    <EditText
+        android:id="@+id/password_old"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:ems="10"
+        android:inputType="textPassword" >
+
+        <requestFocus />
+    </EditText>
+
+    <TextView
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="@string/new_password"
+        android:textAppearance="?android:attr/textAppearanceMedium" />
+
+    <EditText
+        android:id="@+id/password_new"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:ems="10"
+        android:inputType="textPassword" />
+
+    <TextView
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="@string/confirm_new_password"
+        android:textAppearance="?android:attr/textAppearanceMedium" />
+
+    <EditText
+        android:id="@+id/password_confirm"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:ems="10"
+        android:inputType="textPassword" />
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="horizontal" >
+
+        <Button
+            android:id="@+id/submit_password"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="OK" />
+
+        <TextView
+            android:id="@+id/error"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:textColor="@color/error_color" />
+    </LinearLayout>
+
+</LinearLayout>

res/values/strings.xml

@@ -51,4 +51,5 @@
     <string name="old_password">Old password:</string>
     <string name="new_password">New password:</string>
     <string name="confirm_new_password">Confirm new password:</string>
+    <string name="password_changed">Password changed successfully</string>
 </resources>

src/i2p/bote/SetPasswordActivity.java

@@ -1,88 +1,15 @@
 package i2p.bote;
 
-import android.app.ProgressDialog;
-import android.content.Context;
-import android.os.AsyncTask;
 import android.os.Bundle;
 import android.support.v7.app.ActionBarActivity;
-import android.view.View;
-import android.view.inputmethod.InputMethodManager;
-import android.widget.Button;
-import android.widget.EditText;
-import android.widget.TextView;
 
 public class SetPasswordActivity extends ActionBarActivity {
-    TextView error;
-
     @Override
-    protected void onCreate(Bundle savedInstanceState) {
+    public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_set_password);
 
         // Enable ActionBar app icon to behave as action to go back
         getSupportActionBar().setDisplayHomeAsUpEnabled(true);
-
-        final EditText oldField = (EditText) findViewById(R.id.password_old);
-        final EditText newField = (EditText) findViewById(R.id.password_new);
-        final EditText confirmField = (EditText) findViewById(R.id.password_confirm);
-        final Button b = (Button) findViewById(R.id.submit_password);
-        error = (TextView) findViewById(R.id.error);
-
-        b.setOnClickListener(new View.OnClickListener() {
-            @Override
-            public void onClick(View view) {
-                String oldPassword = oldField.getText().toString();
-                String newPassword = newField.getText().toString();
-                String confirmNewPassword = confirmField.getText().toString();
-
-                InputMethodManager imm = (InputMethodManager)getSystemService(Context.INPUT_METHOD_SERVICE);
-                imm.hideSoftInputFromWindow(newField.getWindowToken(), 0);
-
-                new PasswordWaiter().execute(oldPassword, newPassword, confirmNewPassword);
-            }
-        });
-    }
-
-    private class PasswordWaiter extends AsyncTask<String, String, String> {
-        private final ProgressDialog dialog = new ProgressDialog(SetPasswordActivity.this);
-
-        protected void onPreExecute() {
-            dialog.setCancelable(false);
-            dialog.show();
-        }
-
-        protected String doInBackground(String... params) {
-            StatusListener lsnr = new StatusListener() {
-                public void updateStatus(String status) {
-                    publishProgress(status);
-                }
-            };
-            try {
-                I2PBote.getInstance().changePassword(
-                        params[0].getBytes(),
-                        params[1].getBytes(),
-                        params[2].getBytes(),
-                        lsnr);
-                return null;
-            } catch (Throwable e) {
-                cancel(false);
-                return e.getMessage();
-            }
-        }
-
-        protected void onProgressUpdate(String... values) {
-            dialog.setMessage(values[0]);
-        }
-
-        protected void onCancelled(String result) {
-            error.setText(result);
-            dialog.dismiss();
-        }
-
-        protected void onPostExecute(String result) {
-            dialog.dismiss();
-            // Password changed successfully
-            finish();
-        }
     }
 }

src/i2p/bote/SetPasswordFragment.java

@@ -0,0 +1,171 @@
+package i2p.bote;
+
+import i2p.bote.util.RobustAsyncTask;
+import i2p.bote.util.TaskFragment;
+import android.app.Activity;
+import android.content.Context;
+import android.content.Intent;
+import android.os.Bundle;
+import android.support.v4.app.Fragment;
+import android.support.v4.app.FragmentManager;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.view.inputmethod.InputMethodManager;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.TextView;
+import android.widget.Toast;
+
+public class SetPasswordFragment extends Fragment {
+    // Code to identify the fragment that is calling onActivityResult().
+    static final int PASSWORD_WAITER = 0;
+    // Tag so we can find the task fragment again, in another
+    // instance of this fragment after rotation.
+    static final String PASSWORD_WAITER_TAG = "passwordWaiterTask";
+
+    private FragmentManager mFM;
+    Button mSubmit;
+    TextView mError;
+
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        mFM = getFragmentManager();
+        PasswordWaiterFrag f = (PasswordWaiterFrag) mFM.findFragmentByTag(PASSWORD_WAITER_TAG);
+        if (f != null)
+            f.setTargetFragment(this, PASSWORD_WAITER);
+    }
+
+    @Override
+    public View onCreateView(LayoutInflater inflater, ViewGroup container,
+            Bundle savedInstanceState) {
+        return inflater.inflate(R.layout.fragment_set_password, container);
+    }
+
+    @Override
+    public void onViewCreated(View view, Bundle savedInstanceState) {
+        super.onViewCreated(view, savedInstanceState);
+
+        final EditText oldField = (EditText) view.findViewById(R.id.password_old);
+        final EditText newField = (EditText) view.findViewById(R.id.password_new);
+        final EditText confirmField = (EditText) view.findViewById(R.id.password_confirm);
+        mSubmit = (Button) view.findViewById(R.id.submit_password);
+        mError = (TextView) view.findViewById(R.id.error);
+
+        mSubmit.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View view) {
+                String oldPassword = oldField.getText().toString();
+                String newPassword = newField.getText().toString();
+                String confirmNewPassword = confirmField.getText().toString();
+
+                InputMethodManager imm = (InputMethodManager)getActivity().getSystemService(Context.INPUT_METHOD_SERVICE);
+                imm.hideSoftInputFromWindow(newField.getWindowToken(), 0);
+
+                mSubmit.setEnabled(false);
+                mError.setText("");
+
+                PasswordWaiterFrag f = PasswordWaiterFrag.newInstance(oldPassword, newPassword, confirmNewPassword);
+                f.setTask(new PasswordWaiter());
+                f.setTargetFragment(SetPasswordFragment.this, PASSWORD_WAITER);
+                mFM.beginTransaction()
+                    .replace(R.id.password_waiter_frag, f, PASSWORD_WAITER_TAG)
+                    .addToBackStack(null)
+                    .commit();
+            }
+        });
+    }
+
+    @Override
+    public void onActivityResult(int requestCode, int resultCode, Intent data) {
+        if (requestCode == PASSWORD_WAITER) {
+            if (resultCode == Activity.RESULT_OK) {
+                Toast.makeText(getActivity(), R.string.password_changed,
+                        Toast.LENGTH_SHORT).show();
+                getActivity().finish();
+            } else if (resultCode == Activity.RESULT_CANCELED) {
+                mSubmit.setEnabled(true);
+                mError.setText(data.getStringExtra("error"));
+            }
+        }
+    }
+
+    public static class PasswordWaiterFrag extends TaskFragment<String, String, String> {
+        TextView mStatus;
+
+        public static PasswordWaiterFrag newInstance(String... params) {
+            PasswordWaiterFrag f = new PasswordWaiterFrag();
+            Bundle args = new Bundle();
+            args.putStringArray("params", params);
+            f.setArguments(args);
+            return f;
+        }
+
+        @Override
+        public View onCreateView(LayoutInflater inflater, ViewGroup container,
+                Bundle savedInstanceState) {
+            View v = inflater.inflate(R.layout.dialog_status, container, false);
+            mStatus = (TextView) v.findViewById(R.id.status);
+
+            return v;
+        }
+
+        @Override
+        public String[] getParams() {
+            Bundle args = getArguments();
+            return args.getStringArray("params");
+        }
+
+        @Override
+        public void updateProgress(String... values) {
+            mStatus.setText(values[0]);
+        }
+
+        @Override
+        public void taskFinished(String result) {
+            super.taskFinished(result);
+
+            if (getTargetFragment() != null) {
+                Intent i = new Intent();
+                i.putExtra("result", result);
+                getTargetFragment().onActivityResult(
+                        getTargetRequestCode(), Activity.RESULT_OK, i);
+            }
+        }
+
+        @Override
+        public void taskCancelled(String error) {
+            super.taskCancelled(error);
+
+            if (getTargetFragment() != null) {
+                Intent i = new Intent();
+                i.putExtra("error", error);
+                getTargetFragment().onActivityResult(
+                        getTargetRequestCode(), Activity.RESULT_CANCELED, i);
+            }
+        }
+    }
+
+    private class PasswordWaiter extends RobustAsyncTask<String, String, String> {
+        protected String doInBackground(String... params) {
+            StatusListener lsnr = new StatusListener() {
+                public void updateStatus(String status) {
+                    publishProgress(status);
+                }
+            };
+            try {
+                I2PBote.getInstance().changePassword(
+                        params[0].getBytes(),
+                        params[1].getBytes(),
+                        params[2].getBytes(),
+                        lsnr);
+                return null;
+            } catch (Throwable e) {
+                cancel(false);
+                return e.getMessage();
+            }
+        }
+    }
+}

src/i2p/bote/util/RobustAsyncTask.java

@@ -0,0 +1,30 @@
+package i2p.bote.util;
+
+import android.os.AsyncTask;
+
+public abstract class RobustAsyncTask<Params, Progress, Result> extends
+        AsyncTask<Params, Progress, Result> {
+    TaskFragment<Params, Progress, Result> mDialog;
+
+    void setFragment(TaskFragment<Params, Progress, Result> fragment) {
+        mDialog = fragment;
+    }
+
+    @Override
+    protected void onProgressUpdate(Progress... values) {
+        if (mDialog != null)
+            mDialog.updateProgress(values);
+    }
+
+    @Override
+    protected void onPostExecute(Result result) {
+        if (mDialog != null)
+            mDialog.taskFinished(result);
+    }
+
+    @Override
+    protected void onCancelled(Result result) {
+        if (mDialog != null)
+            mDialog.taskCancelled(result);
+    }
+}

src/i2p/bote/util/TaskFragment.java

@@ -0,0 +1,69 @@
+package i2p.bote.util;
+
+import android.os.Bundle;
+import android.support.v4.app.DialogFragment;
+
+public class TaskFragment<Params, Progress, Result> extends DialogFragment {
+    RobustAsyncTask<Params, Progress, Result> mTask;
+
+    public void setTask(RobustAsyncTask<Params, Progress, Result> task) {
+        mTask = task;
+        mTask.setFragment(this);
+    }
+
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        // Retain this instance so it isn't destroyed
+        setRetainInstance(true);
+
+        // Start the task
+        if (mTask != null)
+            mTask.execute(getParams());
+    }
+
+    // This is to work around what is apparently a bug. If you don't have it
+    // here the dialog will be dismissed on rotation, so tell it not to dismiss.
+    @Override
+    public void onDestroyView() {
+        if (getDialog() != null && getRetainInstance())
+            getDialog().setDismissMessage(null);
+        super.onDestroyView();
+    }
+
+    @Override
+    public void onResume()
+    {
+        super.onResume();
+        // This is a little hacky, but we will see if the task has finished
+        // while we weren't in this activity, and then we can dismiss ourselves.
+        if (mTask == null)
+            dismiss();
+    }
+
+    public Params[] getParams() {
+        return null;
+    }
+
+    public void updateProgress(Progress... values) {}
+
+    public void taskFinished(Result result) {
+        finishTask();
+    }
+
+    public void taskCancelled(Result result) {
+        finishTask();
+    }
+
+    private void finishTask() {
+        // Make sure we check if it is resumed because we will crash if trying
+        // to dismiss the dialog after the user has switched to another app.
+        if (isResumed())
+            dismiss();
+
+        // If we aren't resumed, setting the task to null will allow us to
+        // dismiss ourselves in onResume().
+        mTask = null;
+    }
+}