tag should specify a target API level Warning

Android app setup preferences, settings, open, read, write, onStop(), onPause(), getSharedPreferences(), SharedPreferences.Editor getInt(), getBoolean(), getString() , putInt(), putString(), putBoolean() example source code.

import android.content.SharedPreferences;

public class MainClass extends Activity {
  public static final String PREFERENCES_NAME = "MyPrefsFile";
  String myNewString;
  int myNewInt;
  Boolean myNewBool;


   @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // read old settings if exist
      SharedPreferences settings = getSharedPreferences(PREFERENCES_NAME, 0);
			
     String sDefault = "Hello!";
      String sStringFromPrefFile = settings.getString("myString", sDefault); // new text  or default Hello!
          
      int nDefaultIndex = 2; //
      int nIndexFromPrefFile = settings.getInt("myInt", nDefaultIndex); // 4 or default 2
			
      Boolean bDefault = false;
      Boolean bFromPrefFile = settings.getBoolean("silentMode", bDefault); // true or default false
        
        
        // new settings will saved in onStop or onPause
        myNewString = "new text";
        myNewInt = 4;
        myNewBool = true;
     }   

    @Override
    protected void onPause() {
    	super.onPause();
        Toast.makeText(getApplicationContext(), "onPause "
        		, Toast.LENGTH_SHORT).show();

    	savePreferences();
    }
    
    @Override
    protected void onStop() {
    	super.onStop();
    	savePreferences();
    }
    /**save settings*/	
    public void savePreferences(){
    	try {
    		SharedPreferences settings = getSharedPreferences(PREFERENCES_NAME, 0);
    		SharedPreferences.Editor editor = settings.edit();
 
    		editor.putString("myString", myNewString);
     		editor.putInt("nMyInt", myNewInt);
    		editor.putBoolean("silentMode", myNewBool); // 
    		
    		editor.commit();
    	} catch (Exception e) {
    		// TODO Auto-generated catch block
    		e.printStackTrace();
    	}
    	
    }	
}

Unable to resolve target android-7
Try this solution:
Select project from tree (project explorer)
- right click on project
- properties
- select Android from tree
- change Project Build Target to higher (or change project build target)
- selct from menu: Project-Clean ( select your project - OK)

Get assets folder files to array of strings.
Its show files in assets folder and sub folders:

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        final AssetManager assetManager = getAssets();
        try {
			// for assets folder add empty string
                        String[] filelist = assetManager.list("");
                        // for assets/subFolderInAssets add only subfolder name
                        String[] filelistInSubfolder = assetManager.list("subFolderInAssets");
			if (filelist == null) {
			    // dir does not exist or is not a directory
			} else {
			    for (int i=0; i<filelist.length; i++) {
			        // Get filename of file or directory
			        String filename = filelist[i];
			    }
			}
                     
                        // if(filelistInSubfolder == null) ............  

		} catch (IOException e) {
			e.printStackTrace();
		}
     }

How set rounded corners and own styles ActivityMy.java

Button btn.setBackgroundResource(R.drawable.back_button_answer);

\res\drawable\back_button_answer.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="//schemas.android.com/apk/res/android" android:shape="rectangle" >
   <corners android:radius="10dip" />
   <!-- background -->
   
   <gradient
                android:startColor="#D6D7D6"
                android:centerColor="#E2E2E2"
                android:centerY="0.75"
                android:endColor="#D6D7D6"
                android:angle="270"
        />
   
   <stroke android:width="2dip" android:color="#fff"/>
</shape>

Call requires API level 16 (current min is 4): android
Change The SDK version in AndroidManifest.xml to higher

<uses-sdk android:minSdkVersion="4" />
// 
<uses-sdk android:minSdkVersion="8" />