Java tutorial
/* * Copyright (C) 2016 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.example.android.petsdb; import android.app.AlertDialog; import android.app.LoaderManager; import android.content.ContentValues; import android.content.CursorLoader; import android.content.DialogInterface; import android.content.Intent; import android.content.Loader; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.net.Uri; import android.os.Bundle; import android.support.v4.app.NavUtils; import android.support.v7.app.AppCompatActivity; import android.text.TextUtils; import android.view.Menu; import android.view.MenuItem; import android.view.MotionEvent; import android.view.View; import android.widget.AdapterView; import android.widget.ArrayAdapter; import android.widget.EditText; import android.widget.Spinner; import android.widget.Toast; import com.example.android.petsdb.data.PetsContract.PetsEntry; import com.example.android.petsdb.data.PetsDBHelper; /** * Allows user to create a new pet or edit an existing one. */ public class EditorActivity extends AppCompatActivity implements LoaderManager.LoaderCallbacks<Cursor> { /** EditText field to enter the pet's name */ private EditText mNameEditText; /** EditText field to enter the pet's breed */ private EditText mBreedEditText; /** EditText field to enter the pet's weight */ private EditText mWeightEditText; /** EditText field to enter the pet's gender */ private Spinner mGenderSpinner; /** * Gender of the pet. The possible values are: * 0 for unknown gender, 1 for male, 2 for female. */ private int mGender = 0; private static final int EXISTING_PET_LOADER = 1; private Uri mCurrentPetUri; private boolean mPetHasChanged = false; /** * OnTouchListener that listens for any user touches on a View, implying that they are modifying * the view, and we change the mPetHasChanged boolean to true. */ private View.OnTouchListener mTouchListener = new View.OnTouchListener() { @Override public boolean onTouch(View view, MotionEvent motionEvent) { mPetHasChanged = true; return false; } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_editor); Intent intent = getIntent(); Uri currentPetUri = intent.getData(); mCurrentPetUri = currentPetUri; if (currentPetUri == null) { setTitle("Add a Pet"); invalidateOptionsMenu(); } else { setTitle(getString(R.string.editor_activity_title_edit_pet)); getLoaderManager().initLoader(EXISTING_PET_LOADER, null, this); } // Find all relevant views that we will need to read user input from mNameEditText = (EditText) findViewById(R.id.edit_pet_name); mBreedEditText = (EditText) findViewById(R.id.edit_pet_breed); mWeightEditText = (EditText) findViewById(R.id.edit_pet_weight); mGenderSpinner = (Spinner) findViewById(R.id.spinner_gender); // Setup OnTouchListeners on all the input fields, so we can determine if the user // has touched or modified them. This will let us know if there are unsaved changes // or not, if the user tries to leave the editor without saving. mNameEditText.setOnTouchListener(mTouchListener); mBreedEditText.setOnTouchListener(mTouchListener); mWeightEditText.setOnTouchListener(mTouchListener); mGenderSpinner.setOnTouchListener(mTouchListener); setupSpinner(); } /** * Setup the dropdown spinner that allows the user to select the gender of the pet. */ private void setupSpinner() { // Create adapter for spinner. The list options are from the String array it will use // the spinner will use the default layout ArrayAdapter genderSpinnerAdapter = ArrayAdapter.createFromResource(this, R.array.array_gender_options, android.R.layout.simple_spinner_item); // Specify dropdown layout style - simple list view with 1 item per line genderSpinnerAdapter.setDropDownViewResource(android.R.layout.simple_dropdown_item_1line); // Apply the adapter to the spinner mGenderSpinner.setAdapter(genderSpinnerAdapter); // Set the integer mSelected to the constant values mGenderSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() { @Override public void onItemSelected(AdapterView<?> parent, View view, int position, long id) { String selection = (String) parent.getItemAtPosition(position); if (!TextUtils.isEmpty(selection)) { if (selection.equals(getString(R.string.gender_male))) { mGender = PetsEntry.GENDER_MALE; // Male } else if (selection.equals(getString(R.string.gender_female))) { mGender = PetsEntry.GENDER_FEMALE; // Female } else { mGender = PetsEntry.GENDER_UNKNWON; // Unknown } } } // Because AdapterView is an abstract class, onNothingSelected must be defined @Override public void onNothingSelected(AdapterView<?> parent) { mGender = 0; // Unknown } }); } private void insertPet() { String petName = mNameEditText.getText().toString().trim(); String petBreed = mBreedEditText.getText().toString().trim(); int petGender = mGender; int petWeight = Integer.parseInt(mWeightEditText.getText().toString().trim()); if (mCurrentPetUri == null && TextUtils.isEmpty(petName) && TextUtils.isEmpty(petBreed) && TextUtils.isEmpty(getString(petWeight))) { return; } PetsDBHelper mDbHelper = new PetsDBHelper(this); SQLiteDatabase db = mDbHelper.getWritableDatabase(); ContentValues values = new ContentValues(); values.put(PetsEntry.COLUMN_NAME, petName); values.put(PetsEntry.COLUMN_BREED, petBreed); values.put(PetsEntry.COLUMN_GENDER, petGender); int weight = 0; if (!TextUtils.isEmpty(mWeightEditText.getText().toString().trim())) { weight = Integer.parseInt(mWeightEditText.getText().toString().trim()); } values.put(PetsEntry.COLUMN_WEIGHT, weight); // long newRowId = db.insert(PetsEntry.TABLE_NAME, null, values); // // if (newRowId == -1) { // Toast.makeText(this, "Error with saving data", Toast.LENGTH_SHORT).show(); // } // // else { // Toast.makeText(this, "Pet saved with Row id: "+ newRowId, Toast.LENGTH_SHORT).show(); // } Uri newUri = getContentResolver().insert(PetsEntry.CONTETNT_URI, values); if (newUri == null) { Toast.makeText(this, getString(R.string.editor_insert_pet_failed), Toast.LENGTH_SHORT).show(); } else { Toast.makeText(this, getString(R.string.editor_insert_pet_successful), Toast.LENGTH_SHORT).show(); ; } finish(); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu options from the res/menu/menu_editor.xml file. // This adds menu items to the app bar. getMenuInflater().inflate(R.menu.menu_editor, menu); return true; } @Override public boolean onPrepareOptionsMenu(Menu menu) { super.onPrepareOptionsMenu(menu); // If this is a new pet, hide the "Delete" menu item. if (mCurrentPetUri == null) { MenuItem menuItem = menu.findItem(R.id.action_delete); menuItem.setVisible(false); } return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // User clicked on a menu option in the app bar overflow menu switch (item.getItemId()) { // Respond to a click on the "Save" menu option case R.id.action_save: if (mCurrentPetUri == null) { insertPet(); finish(); } else { String petName = mNameEditText.getText().toString().trim(); String petBreed = mBreedEditText.getText().toString().trim(); int petGender = mGender; int petWeight = Integer.parseInt(mWeightEditText.getText().toString().trim()); ContentValues values = new ContentValues(); values.put(PetsEntry.COLUMN_NAME, petName); values.put(PetsEntry.COLUMN_BREED, petBreed); values.put(PetsEntry.COLUMN_GENDER, petGender); values.put(PetsEntry.COLUMN_WEIGHT, petWeight); int rowsAffected = getContentResolver().update(mCurrentPetUri, values, null, null); if (rowsAffected == 0) { Toast.makeText(this, getString(R.string.editor_update_pet_failed), Toast.LENGTH_SHORT).show(); } else { Toast.makeText(this, getString(R.string.editor_update_pet_successful), Toast.LENGTH_SHORT) .show(); } finish(); } return true; // Respond to a click on the "Delete" menu option case R.id.action_delete: showDeleteConfirmationDialog(); return true; // Respond to a click on the "Up" arrow button in the app bar case android.R.id.home: // Navigate back to parent activity (CatalogActivity) if (!mPetHasChanged) { NavUtils.navigateUpFromSameTask(EditorActivity.this); return true; } // Otherwise if there are unsaved changes, setup a dialog to warn the user. // Create a click listener to handle the user confirming that // changes should be discarded. DialogInterface.OnClickListener discardButtonClickListener = new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialogInterface, int i) { // User clicked "Discard" button, navigate to parent activity. NavUtils.navigateUpFromSameTask(EditorActivity.this); } }; // Show a dialog that notifies the user they have unsaved changes showUnsavedChangesDialog(discardButtonClickListener); return true; } return super.onOptionsItemSelected(item); } @Override public Loader<Cursor> onCreateLoader(int i, Bundle bundle) { // Since the editor shows all pet attributes, define a projection that contains // all columns from the pet table String[] projection = { PetsEntry._ID, PetsEntry.COLUMN_NAME, PetsEntry.COLUMN_BREED, PetsEntry.COLUMN_GENDER, PetsEntry.COLUMN_WEIGHT }; // This loader will execute the ContentProvider's query method on a background thread return new CursorLoader(this, // Parent activity context mCurrentPetUri, // Query the content URI for the current pet projection, // Columns to include in the resulting Cursor null, // No selection clause null, // No selection arguments null); // Default sort order } @Override public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) { if (cursor.moveToFirst()) { // Find the columns of pet attributes that we're interested in int nameColumnIndex = cursor.getColumnIndex(PetsEntry.COLUMN_NAME); int breedColumnIndex = cursor.getColumnIndex(PetsEntry.COLUMN_BREED); int genderColumnIndex = cursor.getColumnIndex(PetsEntry.COLUMN_GENDER); int weightColumnIndex = cursor.getColumnIndex(PetsEntry.COLUMN_WEIGHT); // Extract out the value from the Cursor for the given column index String name = cursor.getString(nameColumnIndex); String breed = cursor.getString(breedColumnIndex); int gender = cursor.getInt(genderColumnIndex); int weight = cursor.getInt(weightColumnIndex); // Update the views on the screen with the values from the database mNameEditText.setText(name); mBreedEditText.setText(breed); mWeightEditText.setText(Integer.toString(weight)); // Gender is a dropdown spinner, so map the constant value from the database switch (gender) { case PetsEntry.GENDER_MALE: mGenderSpinner.setSelection(1); break; case PetsEntry.GENDER_FEMALE: mGenderSpinner.setSelection(2); break; default: mGenderSpinner.setSelection(0); break; } } } @Override public void onLoaderReset(Loader<Cursor> loader) { } @Override public void onBackPressed() { // If the pet hasn't changed, continue with handling back button press if (!mPetHasChanged) { super.onBackPressed(); return; } // Otherwise if there are unsaved changes, setup a dialog to warn the user. // Create a click listener to handle the user confirming that changes should be discarded. DialogInterface.OnClickListener discardButtonClickListener = new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialogInterface, int i) { // User clicked "Discard" button, close the current activity. finish(); } }; // Show dialog that there are unsaved changes showUnsavedChangesDialog(discardButtonClickListener); } private void showUnsavedChangesDialog(DialogInterface.OnClickListener discardButtonClickListener) { // Create an AlertDialog.Builder and set the message, and click listeners // for the postivie and negative buttons on the dialog. AlertDialog.Builder builder = new AlertDialog.Builder(this); builder.setMessage(R.string.unsaved_changes_dialog_msg); builder.setPositiveButton(R.string.discard, discardButtonClickListener); builder.setNegativeButton(R.string.keep_editing, new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { // User clicked the "Keep editing" button, so dismiss the dialog // and continue editing the pet. if (dialog != null) { dialog.dismiss(); } } }); // Create and show the AlertDialog AlertDialog alertDialog = builder.create(); alertDialog.show(); } private void showDeleteConfirmationDialog() { // Create an AlertDialog.Builder and set the message, and click listeners // for the positive and negative buttons on the dialog. AlertDialog.Builder builder = new AlertDialog.Builder(this); builder.setMessage(R.string.delete_dialog_msg); builder.setPositiveButton(R.string.delete, new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { // User clicked the "Delete" button, so delete the pet. deletePet(); } }); builder.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { // User clicked the "Cancel" button, so dismiss the dialog // and continue editing the pet. if (dialog != null) { dialog.dismiss(); } } }); // Create and show the AlertDialog AlertDialog alertDialog = builder.create(); alertDialog.show(); } /** * Perform the deletion of the pet in the database. */ private void deletePet() { if (mCurrentPetUri != null) { int rowsDeleted = getContentResolver().delete(mCurrentPetUri, null, null); if (rowsDeleted == 0) { Toast.makeText(this, getString(R.string.editor_delete_pet_failed), Toast.LENGTH_SHORT).show(); } else { Toast.makeText(this, getString(R.string.editor_delete_pet_successful), Toast.LENGTH_SHORT).show(); } } finish(); } }