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POHow to start an Activity from a java class?
 

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  1. POHow to start an Activity from a java class?
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    <p>I read some posts about how could I call an Android's activity from another Java Class implemented in the application, but no answer to my problem.</p> <p>I have a connection class (<code>Connection.java</code>) which handle the permanent connection needed by the application. This one is constructed with Singleton pattern, so everytime I need connection information or request something I do:</p> <pre><code>final Connection conn = Connection.getConnection(getApplicationContext()); //... Some Code Here conn.methodDoSomethingA(); </code></pre> <p>Then, I have an TabActivity which contains 5 Activities (A, B, C, D, E):</p> <pre><code>public class Tab extends TabActivity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.tab); final Connection conn = Connection.getConnection(getApplicationContext()); intent = new Intent().setClass(this, A.class); spec = tabHost.newTabSpec("A") .setIndicator("A", res.getDrawable(R.drawable.tab_A)) .setContent(intent); tabHost.addTab(spec); //... same for activities B, C, D and E tabHost.setCurrentTab(0); } } </code></pre> <p>Now, I have a public method in Connection class to end connection - <code>endConnection()</code> - which is called several times within the Connection class, for example, when there is Socket Timeout or when receiving a custom message from server informing to end session.</p> <p>The problem starts here - when <code>endConnection()</code> is called it must close sockets and then show a Activity (Theme.Dialog) informing the connection is lost. In order to achieve that I did this, without success:</p> <pre><code>public class Connection { private static Connection connection = null; private Context appContext = null; private Connection(Context appContext) { this.appContext = appContext; } public static Connection getConnection(Context appContext) { if (connection == null) return connection = new Connection(appContext); else return connection; } public void endConnection() { // ... Close sockets and streams - SOME CODE HERE // Show Disconnect Dialog Intent myIntent = new Intent(appContext, Disconnect.class); myIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); appContext.startActivity( myIntent ); } } </code></pre> <p>I also tried to pass the <code>TabActivity</code> context as argument to the <code>Connection.java</code> class and used it instead of <code>appContext</code>, but without success either.</p> <p>I'm getting this errors:</p> <pre><code>W/dalvikvm(9449): threadid=3: thread exiting with uncaught exception (group=0x2aaca228) E/AndroidRuntime(9449): Uncaught handler: thread main exiting due to uncaught exception E/AndroidRuntime(9449): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.test/com.example.test.Disconnect}: java.lang.NullPointerException </code></pre> <p>In other words: - How to start an Activity from a java class?!</p>
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    1. COWhat error are you getting?
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      1. UScoder_For_Life22
    2. COYou wanna intent an Activity form TabActivity ?
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      1. USiSun
    3. COdid you declare all your activities on your Manifest file ? plz add your StackTrace of the error you got
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      1. USHoucine
 

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