Long press by finger on screen
From dialogue select Widgets
Select your widget
Put your widget on the screen

Video tutorial - to add home screen widgets - Android 2.1

If you have to type frequently the same code you can create templates which can be activate via autocomplete with Ctrl + Space.

For example lets assume setOnClickListener body.

To create a template for this select the menu Window->Preferences and Open Java -> Editor -> Templates

Type name of template in Eclipse s editor and pres Ctrl+Space

[caption id="attachment_1114" align="alignleft" width="300" caption="Eclipse-show-template-proposals"][/caption]

Select your template from intellisense help and press Enter or double click on selected item.

[caption id="attachment_1116" align="alignleft" width="300" caption="Eclipse - select your template"][/caption]

	mIdButtonHome.setOnClickListener(new View.OnClickListener() {
		public void onClick(View v) {
			Intent browserIntent = new Intent(Intent.ACTION_VIEW,
					Uri.parse("//android.okhelp.cz/category/software/"));
			startActivity(browserIntent);
		}
	});

Quick help in Eclipse editor: select keyword and press Ctrl+1

UNEXPECTED TOP-LEVEL EXCEPTION:
java.lang.IllegalArgumentException: already added: Lcz/okhelp/MyMathClass;

First try this solution!!!!!
Select your project in project tree and go to the Eclipse menu Project » Clean » Clean projects selected below » select your project and click OK.

If you create *.apk package with proguard sometimes you must back up the project, delete project, and create new project if you are unable to create *.apk file.

Check your AndroidManifest.xml if all Activity is correctly inserted. If you add a library project to Main project you have to insert Activity from library to Main project AndroidManifest.xml


Problem with the library.
I deleted library project from project tree and again put the _library project into the main project. This problem was resolved.
1.)Go to Project » Properties » Java Build Path » Libraries and remove (your projects) click OK.
2.)Go to Project » Clean » Clean projects selected below » select your project and click OK.
3.)Add again your LIBRARY project to your MAIN project Project » Properties » Java Build Path » Libraries.
See image below.

Problem with a *.apk file
If you create signed *.apk, you have to delete previous *.apk from your PC folder.

Activities launcher

public class MainActivity extends ListActivity {
    private class Sample {
        private CharSequence title;
        private Class<? extends Activity> activityClass;

        public Sample(int titleResId, Class<? extends Activity> activityClass) {
            this.activityClass = activityClass;
            this.title = getResources().getString(titleResId);
        }

        @Override
        public String toString() {
            return title.toString();
        }
    }

    private static Sample[] mSamples;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Instantiate the list of samples.
        mSamples = new Sample[]{
                new Sample(R.string.title_first_app, FirstActivity.class),
                new Sample(R.string.title_second_app, SecondActivity.class),
                new Sample(R.string.title_third_app, ThirdActivity.class),
        };

        setListAdapter(new ArrayAdapter<Sample>(this,
                android.R.layout.simple_list_item_1,
                android.R.id.text1,
                mSamples));
    }

    @Override
    protected void onListItemClick(ListView listView, View view, int position, long id) {
        // Launch the sample associated with this list position.
        startActivity(new Intent(MainActivity.this, mSamples[position].activityClass));
    }
}

Environment.getExternalStorageDirectory()+ File.separator

Boolean canWrite =	Environment.getExternalStorageDirectory().canWrite() ;
if(canWrite){
File f = new File(Environment.getExternalStorageDirectory()
                        + File.separator + "my_image.jpg")
f.createNewFile();
}else{

}

AndroidManifest.xml

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />