LessonExample
Android Activity State change handling example:
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import android.content.res.Configuration; import android.os.PersistableBundle; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.EditText; import android.widget.TextView; public class MainActivity extends AppCompatActivity { public static final String TAG = "Android Activity State"; // view private EditText etString; private TextView tvOutput; // string to be saved private String myString; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Always call the superclass first setContentView(R.layout.activity_main); bindView(); // No need to use this if we implement onRestoreInstanceState // Check whether we're recreating a previously destroyed instance // if (savedInstanceState != null) { // // Restore value of members from saved state // //myString = savedInstanceState.getString("mySavedString"); // Log.d(TAG, "onCreate() called with: savedInstanceState = [" + savedInstanceState + "]"); // Log.d(TAG, "onCreate() called with: myString = [" + myString + "]"); // } // else { // // Probably initialize members with default values for a new instance // myString = null; // Log.d(TAG, "onCreate() called with: myString = [" + myString + "]"); // } } private void bindView(){ etString = (EditText) findViewById(R.id.et_string); tvOutput = (TextView) findViewById(R.id.tv_output); } @Override protected void onSaveInstanceState(Bundle outState) { // Always call the superclass so it can save the view hierarchy state super.onSaveInstanceState(outState); // Save UI state changes to the savedInstanceState. // This bundle will be passed to onCreate if the process is // killed and restarted. //Format: outState.putVarType("VarName", "VarValue"); outState.putString("mySavedString", myString); Log.d(TAG, "onSaveInstanceState() called with: outState = [" + outState + "]"); } @Override protected void onRestoreInstanceState(Bundle savedInstanceState) { // Always call the superclass so it can restore the view hierarchy super.onRestoreInstanceState(savedInstanceState); // Restore UI state from the savedInstanceState. // This bundle has also been passed to onCreate. // Format: VarType varName = savedInstanceState.getVarType("VarName"); myString = savedInstanceState.getString("mySavedString"); Log.d(TAG, "onRestoreInstanceState() called with: savedInstanceState = [" + savedInstanceState + "]"); Log.d(TAG, "onRestoreInstanceState() called with: myString = [" + myString + "]"); } public void process(View view){ switch (view.getId()) { case R.id.btn_save: myString = etString.getText().toString(); etString.setText(""); etString.setHint("Type something here"); break; case R.id.btn_show: if (myString != null) tvOutput.setText(myString); else tvOutput.setText("No saved string."); break; case R.id.btn_clear: resetView(); break; } } private void resetView(){ etString.setText(""); etString.setHint("Type something here"); tvOutput.setText(""); } // called when the activity is about to become visible @Override protected void onStart() { super.onStart(); //Log.d(TAG, "onStart() called"); } @Override protected void onRestart() { super.onRestart(); Log.d(TAG, "onRestart() called"); } // called when the activity has become visible @Override protected void onResume() { super.onResume(); //resetView(); Log.d(TAG, "onResume() called"); } // called when another activity is taking focus @Override protected void onPause() { super.onPause(); Log.d(TAG, "onPause() called"); } // called when the activity is no longer visible @Override protected void onStop() { super.onStop(); Log.d(TAG, "onStop() called"); } // called just before the activity is destroyed // Configuration changes during runtime (screen orientation, keyboard availability, and language) also call onDestroy @Override protected void onDestroy() { super.onDestroy(); Log.d(TAG, "onDestroy() called"); } } |
