Android：如何通过按钮启动活动？

Question

Noob Android developer here I'm more graphics than code but thought I'd start doing more coding. Anyway, I have some buttons on my main activity page and I want it so when the button is clicked it opens another class/activity. I've tried all the methods I've looked up and something is still not working, when I click the button in the emulator it just doesn't do anything, does't forcestop or anything just nothing, someone point me in the right direction please.

Code from the main page where the button lives:

public class StartingPoint extends Activity {
protected void onCreate(Bundle aim) {
    super.onCreate(aim);

    setContentView(R.layout.main);

    final Button bSL = (Button) findViewById(R.id.bSongList);
    bSL.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {

            Intent SongList = new Intent(StartingPoint.this, SongList.class);
            StartingPoint.this.startActivity(SongList);
        }
    });
}
}

Manifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="myname.appname"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="10" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.Black.NoTitleBar" >
        <activity
            android:name=".Splash"
            android:label="@string/app_name"
            android:theme="@android:style/Theme.Black.NoTitleBar.Fullscreen" >
            <intent-filter>
                <action android:name="myname.appname.SPLASH" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".StartingPoint"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="myname.appname.STARTINGPOINT" />

                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
        <activity
            android:name=".SongList"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="myname.appname.SONGLIST" />

                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
    </application>

</manifest>

-L

Last 3 lines of logcat just after clicking the button in question.

01-02 21:59:50.473: I/ActivityManager(75): Starting: Intent { cmp=myname.appname/.SongList } from pid 681
01-02 21:59:52.953: I/ActivityManager(75): Displayed myname.appname/.SongList: +2s351ms
01-02 21:59:58.565: D/dalvikvm(348): GC_EXPLICIT freed 8K, 55% free 2591K/5703K,     external 1625K/2137K, paused 520ms

Answer 1

Try this:

Intent songList = new Intent(StartingPoint.this, SongList.class);
startActivity(songList);

Are you getting any errors? You need to add every Activity you create in the manifest. If you have two activities and only the Main in the manifest, that could be you problem.

On second thought, I believe your manifest is wrong. Check this. With the Main (Your starting point) and the Menu which is the second one:

<activity android:name="com.activities.Main">
        <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>  
    </activity>
    <activity android:name="com.activities.Menu"></activity>

Try this manifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="myname.appname"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="10" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.Black.NoTitleBar" >
        <activity
            android:name=".Splash"
            android:label="@string/app_name"
            android:theme="@android:style/Theme.Black.NoTitleBar.Fullscreen" >
            <intent-filter>
                    <action android:name="android.intent.action.MAIN" />
                    <category android:name="android.intent.category.LAUNCHER" />               
            </intent-filter>
        </activity>
        <activity
            android:name=".StartingPoint"
            android:label="@string/app_name" >           
        </activity>
        <activity
            android:name=".SongList"
            android:label="@string/app_name" >            
        </activity>
    </application>

</manifest>

You don't need to add the filter on each activity. I understood that you have only one entry Activity and that is the splash screen. However, you might need to change the manifest to change the ".Splash" and every other Activity to the full path including the package.

Answer 2

// whats your package name for your SongList

as your log cats shows

01-02 21:59:50.473: I/ActivityManager(75): Starting: Intent { cmp=myname.appname/.SongList } from pid 681
01-02 21:59:52.953: I/ActivityManager(75): Displayed myname.appname/.SongList: +2s351ms

//use full package name in your activity in manifest.xml

<activity
        android:name="myname.appname.SongList"
        android:label="@string/app_name" >       
    </activity>

Answer 3

Your activity does not start because it has a NullPointerException in it. (Line 10). When you do a findViewById on something that is not in your layout, most likely.

When facing this kind of problems, reading the red lines is usually helpful. It basically says: "Hey! you have a null object in SongList line 10 when you try to start it!"

Edit

ImageView ivlogo = (ImageView) findViewById(R.id.ivsonglogo);
ExpandableListView elv1 = (ExpandableListView) findViewById(R.id.elv1);

This can never work. This is done during the object initialization, much before onCreate is called, therefore much before you have called setContentView.

You must initialize your widgets after having set the view.

Answer 4

Intent SongList = new Intent(StartingPoint.this, SongList.class);
            startActivity(SongList);

and in Manifest type this

 <application .....>
<activity android:name=".CustomSurfaceView"></activity>
</application>

Answer 5

For the code try this:

Intent songListIntent = new Intent(this, SongList.class);
StartingPoint.this.startActivity(songListIntent);

And for manifest:

<activity android:name=".SongList"></activity>