Android commonly used code

Android create option menu in Activity

@Override
public boolean onCreateOptionsMenu(Menu menu) {
	// Inflate the menu; this adds items to the action bar if it is present.
	getMenuInflater().inflate(R.menu.main, menu);
	return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
	// Handle action bar item clicks here. The action bar will
	// automatically handle clicks on the Home/Up button, so long
	// as you specify a parent activity in AndroidManifest.xml.
	int id = item.getItemId();
	if (id == R.id.action_settings) {
		return true;
	}
	return super.onOptionsItemSelected(item);
}

android toast helper class

public class Toaster {
	
	public static void s(Context context, int msg) {
		Toast.makeText(context, msg, Toast.LENGTH_SHORT).show();
	}
	
	public static void l(Context context , int msg) {
		Toast.makeText(context, msg, Toast.LENGTH_LONG).show();
	}
}

download a file from internet and save it to local

	/**
	 * Download a file from the given url and save it to the given file path
	 * @param urlString
	 * @param filepath
	 */
	public void downloadFile(String urlString, String filepath) {
		try {
			URL url = new URL(urlString);
			URLConnection conn = url.openConnection();
			conn.connect();
			InputStream is = conn.getInputStream();
			final int fileSize = conn.getContentLength();
			if (fileSize <= 0) { 
				return;
			}
			if (is == null) { 
				return;
			}

			FileOutputStream fos = new FileOutputStream(filepath); 

			byte buf[] = new byte[1024];
			int numread = 0;
			while ((numread = is.read(buf)) != -1) {
				fos.write(buf, 0, numread);
			}

			is.close();
			fos.close();
		} catch (Exception ex) {
			ex.printStackTrace();
		}
	}

Get HttpResponse body as a String

public static String respondseToString(HttpResponse response) {
	BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
	StringBuilder builder = new StringBuilder();
	for (String line = null; (line = reader.readLine()) != null;) {
	    builder.append(line).append("\n");
	}
	return builder.toString();
}

get webpage content from given url

	public String getContent(String urlString) {
		try {
			URL url = new URL(urlString);
			
			InputStream is = url.openStream();
			ByteArrayOutputStream data = new ByteArrayOutputStream();
			byte[] buffer = new byte[1024];
			int len = 0;
			while ((len = is.read(buffer)) != -1) {
				data.write(buffer, 0, len);
			}
			is.close();
			String str = new String(data.toByteArray(), "utf-8");
			data.close();
			return str;
		} catch (Exception ee) {
			System.out.print("ee:" + ee.getMessage());
		}
		return null;
	}

go to googleplay

private void toGooglePlay(String packageName) {
	try {
		Intent intent = new Intent(Intent.ACTION_VIEW);
		intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
		intent.setData(Uri.parse("market://details?id=" + packageName));
		startActivity(intent);
	} catch (ActivityNotFoundException e) {
		Toast.makeText(this, R.string.toast_no_market_app, Toast.LENGTH_SHORT).show();
	}
}

Log helper class in android

/**
 * Helper class for android Logcat functions
 * @author chuang
 *
 */
@SuppressLint("DefaultLocale")
public class L {

	private static String TAG = "zyzy";
	private static boolean DEBUG = true; 
	private static final String CLASS_METHOD_LINE_FORMAT = "%s.%s() Line:%d---------%s";
	
	/**
	 * Log debug method.
	 * @param caller the Class that calls this method.
	 * @param msg
	 */
	public static void l() {
		if(DEBUG) {
			StackTraceElement traceElement = Thread.currentThread().getStackTrace()[3];// 从堆栈信息中获取当前被调用的方法信息
			String className = traceElement.getClassName();
			String simpleClassName = className.contains(".")?className.substring(className.lastIndexOf(".")+1):className;
			
			String logText = String.format(CLASS_METHOD_LINE_FORMAT, simpleClassName, traceElement.getMethodName(),
				traceElement.getLineNumber());
			
			Log.d(TAG, logText);
		}
	}
	
	/**
	 * Log debug method.
	 * @param caller the Class that calls this method.
	 * @param msg
	 */
	public static void l(Object msg) {
		if(DEBUG) {
			StackTraceElement traceElement = Thread.currentThread().getStackTrace()[3];// 从堆栈信息中获取当前被调用的方法信息
			String className = traceElement.getClassName();
			String simpleClassName = className.contains(".")?className.substring(className.lastIndexOf(".")+1):className;
			
			String logText = String.format(CLASS_METHOD_LINE_FORMAT, simpleClassName, traceElement.getMethodName(),
				traceElement.getLineNumber(), msg.toString());
			
			Log.d(TAG, logText);
		}
	}
	
	public static void trace() {
		StackTraceElement[] traceElements = Thread.currentThread().getStackTrace();
		Log.d(TAG, "trace-------------------------------------------------------------------------");
		int len = traceElements.length;
		for (int i=len-1; i>=0; i--) {
			StackTraceElement traceElement = traceElements[i];
			String logText = String.format(CLASS_METHOD_LINE_FORMAT, traceElement.getClassName(), traceElement.getMethodName(),
			traceElement.getLineNumber(), traceElement.getFileName());
			Log.d(TAG, logText);// 打印Log
		}
		Log.d(TAG, "end trace-------------------------------------------------------------------------");
	}
	
}

Make project work with androidannotation in AndroidStudio

//START: add this block
buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        // replace with the current version of the Android plugin
        classpath 'com.android.tools.build:gradle:0.12.1'
        // the latest version of the android-apt plugin
        classpath 'com.neenbedankt.gradle.plugins:android-apt:1.4'
    }
}
//END

apply plugin: 'com.android.application'

//START: Add this line
apply plugin: 'com.neenbedankt.android-apt'
//END

android {
    compileSdkVersion 19
    buildToolsVersion "20.0.0"

    defaultConfig {
        applicationId "com.chriszou.studyharder"
        minSdkVersion 14
        targetSdkVersion 19
    }

    buildTypes {
        release {
            runProguard false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
        }
    }
}

dependencies {
    //START: Add these two lines
    apt "org.androidannotations:androidannotations:3.0.1"        
    compile "org.androidannotations:androidannotations-api:3.0.1"
    //END 
    compile project(':androidlibs')
}

//START: Add this block
apt {
    arguments {
        resourcePackageName android.defaultConfig.applicationId
        androidManifestFile variant.processResources.manifestFile
    }
}
//END

singleton example

public class Singleton {

    private volatile static Singleton singleInstance;
    private Singleton() {
    }
    public static Singleton getInstance() {
        if(singleInstance==null) {
            synchronized(Singleton.class) {
                if(singleInstance==null) {
                    singleInstance = new Singleton();
                }
            }
        }
        return singleInstance;
    }
}

write string to file

	public void writeToFile(String str) {
		BufferedWriter writer = null;
		try {
			writer = new BufferedWriter(new FileWriter("filename.txt"));
			writer.write(str);
		} catch (IOException e) {
			L.l("get ex wrting file");
			e.printStackTrace();
		} finally {
			try {
				if (writer != null) {
					writer.close();
				}
			} catch (IOException e) {
			}
		}
	}