Develop Reference

Method stops running after switching activities

In this app the users score is supposed to increase every second or so, and they can use that score and buy upgrades from the second Activity. When the user starts the app the program works fine, but when they go from the first activity to the second and back it stops updating the textview with the score that increases every second. Can you guys explain whats going on?
package com.example.navjeevenmann.mytycoon;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
private Button myButton;
private int Counter;
private Button myButton2;
private TextView myTextView;
Handler handler = new Handler();
private int add = 1;
#Override
protected void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.activity_main);
super.onCreate(savedInstanceState);
Bundle bundle = getIntent().getExtras();
if (bundle != null) {
if (bundle.containsKey("Count")) {
Counter = bundle.getInt("Count");
}
if (bundle.containsKey("Add")) {
add = bundle.getInt("Add");
}
}
myButton = (Button) findViewById(R.id.button);
myButton2 = (Button) findViewById(R.id.button2);
myTextView = (TextView) findViewById(R.id.textView);
myButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Counter = ButtonCounter(Counter);
}
});
myButton2.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(getApplicationContext(),
SecondActivity.class);
intent.putExtra("Count", Counter);
startActivity(intent);
}
});
handler.postDelayed(new Runnable() {
#Override
public void run() {
Counter= AutoCounter(Counter, add);
Display(Counter);
handler.postDelayed(this, 1000);
}
},100);
}
public int ButtonCounter(int Counter) {
Counter += 1;
return Counter;
}
public int AutoCounter(int Counter, int add) {
Counter += add;
return Counter;
}
public void Display(int Counter) {
String man = String.valueOf(Counter);
myTextView.setText("$" + man);
}
}

You start the counting handler only inside onCreate() method.
When you go back from SecondActivity to MainActivity the onResume() method is called, So
You need to start the counting inside onResume() method.
P.S Make sure to check for nulls before updating you UI from postDelay().
Your Activity might be destroyed by the time the code runs, make sure your TextView is not null before updating.

Android app auto increment a value by 1 with some delay

This is a part of an app that I am trying to make. I am trying to make a delay that can be set by the user so after each +1 it delays with 500 milliseconds, but soon I figured that i don't even know how to add a simple build in delay, I tried with delay(1000); it gave me Can not resolve method delay(int) then with sleep(1000); same error, then with TimeUnit.SECONDS.sleep(1); and Thread.sleep(1); nothing worked I am missing something fundamental, maybe I need to import something ? this is the whole program
if (v == swt1){
while (counter<2100000000) {
counter++;
}
scoreText.setText(Integer.toString(counter));
scoreText.setBackgroundColor(Color.BLACK);
}
Activity:
package counter.test.my.simplecount;
import android.os.Bundle;
import android.util.TypedValue;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Switch;
import android.widget.TextView;
import android.app.Activity;
import android.graphics.Color;
public class MainActivity extends Activity implements OnClickListener {
Button btn1;
Button btn2;
Button btn3;
Switch swt1;
TextView textTitle;
EditText scoreText;
int counter = 0;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
btn1 = (Button)findViewById(R.id.button);
btn2 = (Button)findViewById(R.id.button2);
btn3 = (Button)findViewById(R.id.button3);
swt1 = (Switch)findViewById(R.id.switch1);
scoreText = (EditText)findViewById(R.id.editText);
textTitle = (TextView)findViewById(R.id.textView);
btn1.setOnClickListener(this);
btn2.setOnClickListener(this);
btn3.setOnClickListener(this);
textTitle.setTextSize(TypedValue.COMPLEX_UNIT_SP, 34);
}
#Override
public void onClick(View v) {
if (v == btn1){
counter++;
scoreText.setText(Integer.toString(counter));
scoreText.setBackgroundColor(Color.CYAN);
}
if (v == btn2){
counter--;
scoreText.setText(Integer.toString(counter));
scoreText.setBackgroundColor(Color.GREEN);
}
if (v == btn3){
counter = 0;
scoreText.setText(Integer.toString(counter));
scoreText.setBackgroundColor(Color.RED);
if (v == swt1){
while (counter<2100000000) {
counter++;
}
scoreText.setText(Integer.toString(counter));
scoreText.setBackgroundColor(Color.RED);
}
}
}
}

You can use Handler() for delay like
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
//Your Aftre delay code
}
},500);
Remember to import this:
import android.os.Handler;

Use the "Handler" with "Runnable" to auto increment a value continuously at some time delay. Here i used "1sec" time dealy.
Find below code snippet for your requirement.
Runnable runnable;
Handler handler;
int delayTimeSec = 1000; //1 Sec
handler = new Handler();
runnable = new Runnable(){
#Override
public void run() {
// Your auto increment logic...
handler.postDelayed(runnable, delayTimeSec);
}
}
handler.postDelayed(runnable, delayTimeSec);

Use thread instead of handler if you have got background tasks.
new Thread(new Runnable() {
#Override
public void run() {
///background calculations
try {
Thread.sleep(1000L);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
runOnUiThread(new Runnable() {
#Override
public void run() {
//main thread task to update user interface
}
});
}
}).start();

Unable to update the UI using the message from the handler

Hello everyone, I am new to android application development. I have written and code and trying to update the UI from the message obtained from handler. I have tried to debug the code but i couldn't find what the error is. please help me out. Thank you.
package com.threadcommunicationexample;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends Activity implements OnClickListener {
Button Click;
TextView Message;
Handler Mrmessenger;
int Counter = 0;
/*
*Initialisation area....
*/
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Click = (Button) findViewById(R.id.ClickButton);
Message = (Button) findViewById(R.id.TextView);
Click.setOnClickListener(this);
}
#Override
public void onClick(View v) {
// Operation to be performed after the button click
Runnable myThreadRunner = new Runnable() {
#Override
public void run() {
// Saving the text in bundle and passing it to handler ....
while (Counter < 100) {
try {
Thread.sleep(100);
Message msg = Mrmessenger.obtainMessage();
Bundle myBundle = new Bundle();
myBundle.putString("Communication", "Loading....");
msg.setData(myBundle);
//Sending the bundle to Handler
Mrmessenger.sendMessage(msg);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Mrmessenger = new Handler() {
public void handleMessage(final Message msg) {
Mrmessenger.post(new Runnable() {
// Getting the message from the handler and updating it using textview
#Override
public void run() {
Bundle ComBundle = msg.getData();
// TODO Auto-generated method stub
String myMessage = ComBundle
.getString("Communication");
Message.setText(myMessage);
}
});
}
};
Counter++;
}
}
};
Thread myRunner = new Thread(myThreadRunner);
//creating a thread and passing the runnable object.
myRunner.start();
}
}

For one thing, the line
Message msg = Mrmessenger.obtainMessage();
will fail since you don't initialize Mrmessenger until a few lines later.
Would recommend you use AsyncTask for this type of thing; it deals with all of the threading so you don't have to.
Also: per Java conventions, variable names should start with a lowercase letter, class names start with an uppercase letter. This would make your code easier for others to read.

the problem with your code is, that the run method in your handler is called on another thread than the main / ui thread.
To make the code working you can use the following code..
runOnUiThread(new Runnable() {
public void run() {
Message.setText(myMessage);
}
});
..to run the ui update explicitly on the ui thread.

Added textview code crashed the application in emulator

I am working on a homework project that requires to have a textview counter along with an existing progress bar. I added the textview code to java file and main.xml. When I run it in the emulator I get "The application xxx has stopped unexpectedly" message. I have not been able to figure out the cause. Here is my code:
(Code indentation is not entirely proper. I will strive to make it so)
Source file:
package com.mypackage;
import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class MyButtonActivity extends Activity {
static final int PROGRESS_DIALOG = 0;
Button button;
ProgressThread progressThread;
ProgressDialog progressDialog;
TextView Int;
/** Called when the activity is first created. */
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Int = (TextView)findViewById(R.id.Int);
// Setup the button that starts the progress dialog
button = (Button) findViewById(R.id.myButton);
button.setOnClickListener(new Button.OnClickListener(){
public void onClick(View v) {
// Show dialog managed by this activity
showDialog(PROGRESS_DIALOG);
}
});
}
// Callback for creating dialogs that are managed (saved and restored)
// for you by the activity.
protected Dialog onCreateDialog(int id) {
switch(id) {
case PROGRESS_DIALOG:
progressDialog = new ProgressDialog(MyButtonActivity.this);
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setMessage("Loading...");
// Create and start the handler
progressThread = new ProgressThread(handler);
progressThread.start();
return progressDialog;
default:
return null;
}
}
// Define the Handler that receives messages from the thread and update
// the progress
final Handler handler = new Handler() {
public void handleMessage(Message msg) {
int total = msg.getData().getInt("total");
progressDialog.setProgress(total);
Int.setText(String.valueOf(total));
if (total >= 100){
dismissDialog(PROGRESS_DIALOG);
progressThread.setState(ProgressThread.STATE_DONE);
}
}
};
/** Nested class that performs progress calculations (counting) */
private class ProgressThread extends Thread {
Handler mHandler;
final static int STATE_DONE = 0;
final static int STATE_RUNNING = 1;
int mState;
int total;
ProgressThread(Handler h) {
mHandler = h;
}
public void run() {
mState = STATE_RUNNING;
total = 0;
while (mState == STATE_RUNNING) {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
Log.e("ERROR", "Thread Interrupted");
}
Message msg = mHandler.obtainMessage();
Bundle b = new Bundle();
b.putInt("total", total);
msg.setData(b);
mHandler.sendMessage(msg);
total++;
}
}
/* sets the current state for the thread,
* used to stop the thread */
public void setState(int state) {
mState = state;
}
}
I only added a few lines to existing code (including a textview to main.xml). So is it more involved than simply adding textview code to implement the textview counter? Given that it is one of first projects in my intro level course, I think simply adding a textview should satisfy the requirement. Please enlighten. Thanks!

I tested your code and it worked for me! Did you try to:
Under Eclipse bar Project->Clean Project
Right click on your project Android Tools->Fix Project Properties

Changing Text Alignment in ProgressDialog

I have problem that how to change text inside the progressdialog (basically having STYLE_HORIZONTAL as in figure) (Using Android 1.6)
to text shown in figure.
Please help out in this case.
My code about the progressdialog refers like this:-
mProgressDialog = new ProgressDialog(PDFActivity.this);
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
mProgressDialog.setTitle(R.string.msgDownloadingWait);
mProgressDialog.setMessage(getResources().getString(
R.string.msgDownloading));
// User is not allowed to cancel the download operation.
mProgressDialog.setCancelable(false);
mProgressDialog.setMax(serverFileCount);
mProgressDialog.show();
Thanks in advance.

I got the answer related to this stuff some days back(but updating it today as got some free time).
Here the code that I have used for making this stuff best.I achieved above thing by Custom Dialog.Firstly here the code of activity from which I called the class of Custom Dialog.
import android.app.Activity;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.widget.ProgressBar;
import android.widget.TextView;
public class ProgressThread extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
MyDialog dialog = new MyDialog(this);
dialog.show();
}
}
Now the code related to the Custom Dialog. Here I have used ProgressBar & TextViews in CustomDialog & made calculations on basis on download which in turn updates TextViews.The example used here updates the textviews & progressbar in dummy manner.You change that as per your need.
import android.app.Dialog;
import android.content.Context;
import android.graphics.Color;
import android.os.Handler;
import android.os.Message;
import android.widget.ProgressBar;
import android.widget.TextView;
public class MyDialog extends Dialog {
public static final int STATUS_UPDATE = 101;
public static final int STATUS_COMPLETE = 100;
ProgressBar progressBar;
TextView textView;
TextView percent;
int increment;
int progress;
public MyDialog(Context context) {
super(context);
setContentView(R.layout.progressbar);
setDialog();
}
private void setDialog() {
setTitle("Downloading Files....");
textView = (TextView) findViewById(R.id.textProgress);
progressBar = (ProgressBar) findViewById(R.id.progress_horizontal);
percent = (TextView) findViewById(R.id.textPercentage);
percent.setTextColor(Color.WHITE);
textView.setTextColor(Color.WHITE);
progressBar.setProgressDrawable(getContext().getResources()
.getDrawable(R.drawable.my_progress));
progressBar.setIndeterminate(false);
// set the maximum value
progressBar.setMax(1315);
launcherThread();
}
private void launcherThread() {
LoaderThread loaderThread = new LoaderThread();
loaderThread.start();
LauncherThread launcherThread = new LauncherThread();
launcherThread.start();
}
private class LoaderThread extends Thread {
#Override
public void run() {
try {
while (progressBar.getProgress() < progressBar.getMax()) {
// wait 500ms between each update
Thread.sleep(100);
increment++;
// active the update handler
progressHandler.sendEmptyMessage(STATUS_UPDATE);
}
progressHandler.sendEmptyMessage(STATUS_COMPLETE);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
// handler for the background updating
Handler progressHandler = new Handler() {
public void handleMessage(Message msg) {
switch (msg.what) {
case STATUS_UPDATE:
progressBar.setProgress(increment);
float value = increment / 1315F;
percent.setText(" " + ((int) (value * 100)) + "%");
System.out.println(value * 100);
textView.setText(String.valueOf(progressBar.getProgress())
.concat(" / " + progressBar.getMax()));
break;
case STATUS_COMPLETE:
dismiss();
}
}
};
private class LauncherThread extends Thread {
#Override
public void run() {
progressHandler.sendMessage(progressHandler.obtainMessage());
progressHandler.sendEmptyMessage(0);
}
}
}