Trouble Shooting : Android Programming @DrBFraser

Uploaded February 2013 | Updated September 2026, 2 weeks ago

A demonstration how to fix many different types of errors in an Android project.

Included:
- Using the Eclipse views: Console, Problems, LogCat
- Not closing an XML tag
- Incorrect string resource in XML
- Importing Android.R
- Java compile problems (missing }, incorrect method name)
- Invalid type cast (ImageButton to Button)
- Invalid type cast in a button call-back
- Uses project -- clean
- Shows: right-click, Android Tools -- Fix Project Properties
- Invalid resource naming

$Computation in background w/ AsyncTask: Android Programming How to use an AsyncTask to do calculations in the background of an Android Activity: guesses a number on a background thread while showing updates on the UI. Full code below. // TODO: Change all [[ and ]] to less-than and greater-than (YouTube limitation) package ca.demo.asynctaskdemo; import java.util.Random; import android.app.Activity; import android.os.AsyncTask; import android.os.Bundle; import android.view.View; import android.view.Window; import android.widget.TextView; /** * Demonstration of how to use an AsyncTask by cracking a password. */ public class MainActivity extends Activity { private static final long PASSWORD = 12345; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS); setContentView(R.layout.activity_main); } public void onClick_StartTask(View v) { final long PUBLISH_RATE = 1000; final long RANGE = 1000000; // Start background task PasswordGuesserTask crackerTask = new PasswordGuesserTask(); crackerTask.execute(RANGE, PUBLISH_RATE); } public void displayProgress(String message) { TextView textView = (TextView) findViewById(R.id.txtStatus); textView.setText(message); } public void displayAnswer(long answer) { String message = I know the password: + answer; TextView textView = (TextView) findViewById(R.id.txtFinalAnswer); textView.setText(message); } /* * Background task to crack the password. */ // Generics: // 1. Long: Type of reference(s) passed to doInBackground() // 2. String: Type of reference passed to onProgressUpdate() // 3. Long: Type of reference returned by doInBackground() // Value passed to onPostExecute() // TODO: Change all [[ and ]] to less-than and greater-than (YouTube limitation) private class PasswordGuesserTask extends AsyncTask[[Long, String, Long]] { // Executed on main UI thread @Override protected void onPreExecute() { super.onPreExecute(); MainActivity.this.setProgressBarIndeterminateVisibility(true); } // Run on background thread. @Override protected Long doInBackground(Long... arguments) { // Extract arguments long range = arguments[0]; long publishRate = arguments[1]; long guess = 0; long count = 0; Random rand = new Random(); while (guess != PASSWORD) { guess = Math.abs(rand.nextLong()) % range; count ++; if (count % publishRate 0) { publishProgress( Guess #: + count, Last guess: + guess); } } return guess; } // Executed on main UI thread. @Override protected void onProgressUpdate(String... values) { super.onProgressUpdate(values); String message = ; for (String str : values) { message += str + , ; } displayProgress(message); } // Executed on main UI thread @Override protected void onPostExecute(Long result) { super.onPostExecute(result); displayAnswer(result); MainActivity.this.setProgressBarIndeterminateVisibility(false); } } }$

Plain Old Java in Android Studio: Android Programming

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$Context (Option) Menu: Android Programming Demonstration on how to create a context menu (options menu) on the Android phone. Contents: - Understanding the context menu. - Adding items to a context menu. - Responding to click events for the menu: launching another activity or changing text in a TextView. - Adding an icon to the context menu. Sample icons I show are from the Annadroid Tehxseven icon pack: http://www.themebowl.com/annadroid-icons-by-tehkseven.html Code: @Override public boolean onOptionsItemSelected(MenuItem item) { super.onOptionsItemSelected(item); // Dump out the event: String message = Title: + item.getTitle() + , id= + item.getItemId(); Toast.makeText(this, message, Toast.LENGTH_LONG).show(); switch(item.getItemId()) { case R.id.menu_help: startActivity(new Intent(this, HelpActivity.class)); break; case R.id.menu_settings: TextView textView = (TextView) findViewById(R.id.mainText); textView.setText(You changed the text!); } return true; }$

App Bar (ActionBar/Toolbar): Android Programming

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