Android Activity

In Android, Activity is like state  of the application. Each activity has a layout. Activity has a lifecycle.

1. onCreate()

2. onStart()

3. onRestart()

4. onResume()

5. onPause()

6. onStop()

7. onDestroy()

ActivityA.java

package com.example.activitylifecycle;

import android.app.Activity;

import android.os.Bundle;

import android.content.Intent;

import android.view.View;

import android.widget.TextView;

import com.example.activitylifecycle.util.StatusTracker;

import com.example.activitylifecycle.util.Utils;

public class ActivityA extends Activity {

   private String mActivityName;

   private TextView mStatusView;

   private TextView mStatusAllView;

   private StatusTracker mStatusTracker = StatusTracker.getInstance();

   @Override

   public void onCreate(Bundle savedInstanceState) {

       super.onCreate(savedInstanceState);

       setContentView(R.layout.activity_a);

       mActivityName = getString(R.string.activity_a);

       mStatusView = (TextView)findViewById(R.id.status_view_a);

       mStatusAllView = (TextView)findViewById(R.id.status_view_all_a);

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_create));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onStart() {

       super.onStart();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_start));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onRestart() {

       super.onRestart();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_restart));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onResume() {

       super.onResume();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_resume));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onPause() {

       super.onPause();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_pause));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onStop() {

       super.onStop();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_stop));

   }

   @Override

   protected void onDestroy() {

       super.onDestroy();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_destroy));

       mStatusTracker.clear();

   }

   public void startDialog(View v) {

       Intent intent = new Intent(ActivityA.this, DialogActivity.class);

       startActivity(intent);

   }

   public void startActivityB(View v) {

       Intent intent = new Intent(ActivityA.this, ActivityB.class);

       startActivity(intent);

   }

   public void startActivityC(View v) {

       Intent intent = new Intent(ActivityA.this, ActivityC.class);

       startActivity(intent);

   }

 

   public void finishActivityA(View v) {

       ActivityA.this.finish();

   }

}

ActivityB.java

package com.example.activitylifecycle;

import android.app.Activity;

import android.os.Bundle;

import android.content.Intent;

import android.view.View;

import android.widget.TextView;

import com.example.activitylifecycle.util.StatusTracker;

import com.example.activitylifecycle.util.Utils;

public class ActivityB extends Activity {

   private String mActivityName;

   private TextView mStatusView;

   private TextView mStatusAllView;

   private StatusTracker mStatusTracker = StatusTracker.getInstance();

   @Override

   public void onCreate(Bundle savedInstanceState) {

       super.onCreate(savedInstanceState);

       setContentView(R.layout.activity_b);

       mActivityName = getString(R.string.activity_b_label);

       mStatusView = (TextView)findViewById(R.id.status_view_b);

       mStatusAllView = (TextView)findViewById(R.id.status_view_all_b);

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_create));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onStart() {

       super.onStart();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_start));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onRestart() {

       super.onRestart();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_restart));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onResume() {

       super.onResume();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_resume));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onPause() {

       super.onPause();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_pause));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onStop() {

       super.onStop();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_stop));

   }

   @Override

   protected void onDestroy() {

       super.onDestroy();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_destroy));

   }

   public void startDialog(View v) {

       Intent intent = new Intent(ActivityB.this, DialogActivity.class);

       startActivity(intent);

   }

   public void startActivityA(View v) {

       Intent intent = new Intent(ActivityB.this, ActivityA.class);

       startActivity(intent);

   }

   public void startActivityC(View v) {

       Intent intent = new Intent(ActivityB.this, ActivityC.class);

       startActivity(intent);

   }

   public void finishActivityB(View v) {

       ActivityB.this.finish();

   }

}

ActivityC.java

package com.example.android.lifecycle;

import android.app.Activity;

import android.os.Bundle;

import android.content.Intent;

import android.view.View;

import android.widget.TextView;

import com.example.android.lifecycle.util.StatusTracker;

import com.example.android.lifecycle.util.Utils;

public class ActivityC extends Activity {

   private String mActivityName;

   private TextView mStatusView;

   private TextView mStatusAllView;

   private StatusTracker mStatusTracker = StatusTracker.getInstance();

   @Override

   public void onCreate(Bundle savedInstanceState) {

       super.onCreate(savedInstanceState);

       setContentView(R.layout.activity_c);

       mActivityName = getString(R.string.activity_c_label);

       mStatusView = (TextView)findViewById(R.id.status_view_c);

       mStatusAllView = (TextView)findViewById(R.id.status_view_all_c);

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_create));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onStart() {

       super.onStart();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_start));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onRestart() {

       super.onRestart();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_restart));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onResume() {

       super.onResume();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_resume));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onPause() {

       super.onPause();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_pause));

       Utils.printStatus(mStatusView, mStatusAllView);

   }

   @Override

   protected void onStop() {

       super.onStop();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_stop));

   }

   @Override

   protected void onDestroy() {

       super.onDestroy();

       mStatusTracker.setStatus(mActivityName, getString(R.string.on_destroy));

   }

   public void startDialog(View v) {

       Intent intent = new Intent(ActivityC.this, DialogActivity.class);

       startActivity(intent);

   }

   public void startActivityA(View v) {

       Intent intent = new Intent(ActivityC.this, ActivityA.class);

       startActivity(intent);

   }

   public void startActivityB(View v) {

       Intent intent = new Intent(ActivityC.this, ActivityB.class);

       startActivity(intent);

   }

   public void finishActivityC(View v) {

       ActivityC.this.finish();

   }

}

DialogActivity.java

package com.example.activitylifecycle;

import android.app.Activity;

import android.os.Bundle;

import android.view.View;

import android.view.Window;

public class DialogActivity extends Activity {

   @Override

   protected void onCreate(Bundle savedInstanceState) {

       super.onCreate(savedInstanceState);

       requestWindowFeature(Window.FEATURE_NO_TITLE);

       setContentView(R.layout.activity_dialog);

   }

       public void finishDialog(View v) {

       DialogActivity.this.finish();

   }

}

StatusTracker.java

package com.example.activitylifecycle.util;

import java.util.*;

public class StatusTracker {

 private Map<String, String> mStatusMap;

 private List<String> mMethodList;

 private static StatusTracker ourInstance = new StatusTracker();

 private static final String STATUS_SUFFIX = "ed";

 public static StatusTracker getInstance() {

   return ourInstance;

 }

 private StatusTracker() {

   mStatusMap = new LinkedHashMap<String, String>();

   mMethodList = new ArrayList<String>();

 }

 public List<String> getMethodList() {

   return mMethodList;

 }

 public void clear() {

   mMethodList.clear();

   mStatusMap.clear();

 }

   public void setStatus(String activityName, String status) {

   mMethodList.add(activityName + "." + status + "()");

   if (mStatusMap.containsKey(activityName)) mStatusMap.remove(activityName);

   mStatusMap.put(activityName, status);

 }

  public String getStatus(String activityName) {

   String status = mStatusMap.get(activityName);

   status = status.substring(2, status.length());

   // String manipulation to ensure the status value is spelled correctly.

   if (status.endsWith("e")) {

     status = status.substring(0, status.length() - 1);

   }

   if (status.endsWith("p")) {

     status = status + "p";

   }

   status = status + STATUS_SUFFIX;

   return status;

 }

 public Set<String> keySet() {

   return mStatusMap.keySet();

 }

}

Utils.java

package com.example.activitylifecycle.util;

import android.os.Handler;

import android.widget.TextView;

import java.util.List;

public class Utils {

 private static StatusTracker mStatusTracker = StatusTracker.getInstance();

  public static void printStatus(final TextView viewMethods, final TextView viewStatus) {

     Handler handler = new Handler();

     handler.postDelayed(new Runnable() {

       public void run() {

         StringBuilder sbMethods = new StringBuilder();

         List<String> listMethods = mStatusTracker.getMethodList();

         for (String method : listMethods) {

             sbMethods.insert(0, method + "\r\n");

         }

         if(viewMethods != null) {

             viewMethods.setText(sbMethods.toString());

         }

                   StringBuilder sbStatus = new StringBuilder();

         for (String key : mStatusTracker.keySet()) {

           sbStatus.insert(0,key + ": " + mStatusTracker.getStatus(key) + "\n");

         }

         if(viewStatus != null) {

             viewStatus.setText(sbStatus.toString());

         }

       }

     }, 750);

   }

}

Layout ActivityA

Other layout ActivityB and ActivityC also similar to ActivityA.

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

   android:orientation="vertical"

   android:layout_width="match_parent"

   android:layout_height="match_parent"

   android:background="@color/dark_blue"

   android:padding="8dip"

   >

   <TextView android:layout_width="match_parent"

       android:layout_height="wrap_content"

       android:text="@string/activity_a"

       android:gravity="center_horizontal"

       android:textSize="@dimen/font_large"

       android:textColor="@color/light_blue"

       android:paddingBottom="16dip"

       />

   <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

       android:orientation="vertical"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_gravity="center_horizontal"

       >

       <Button

           android:id="@+id/btn_start_b"

           android:layout_height="wrap_content"

           android:layout_width="wrap_content"

           android:text="@string/btn_start_b_label"

           android:onClick="startActivityB"

           />

       <Button

           android:id="@+id/btn_start_c"

           android:layout_height="wrap_content"

           android:layout_width="wrap_content"

           android:text="@string/btn_start_c_label"

           android:layout_toRightOf="@id/btn_start_b"

           android:onClick="startActivityC"

           />

       <Button

           android:id="@+id/btn_finish_a"

           android:layout_height="wrap_content"

           android:layout_width="wrap_content"

           android:text="@string/btn_finish_a_label"

           android:layout_toRightOf="@id/btn_start_c"

           android:onClick="finishActivityA"

           />

       <Button

           android:id="@+id/btn_start_dialog"

           android:layout_height="wrap_content"

           android:layout_width="wrap_content"

           android:text="@string/btn_start_dialog_label"

           android:layout_toRightOf="@id/btn_finish_a"

           android:onClick="startDialog"

           />

   </RelativeLayout>

   <TextView

       android:layout_width="match_parent"

       android:layout_height="wrap_content"

       android:textSize="@dimen/font_medium"

       android:text="@string/lifecycle_method_list"

       android:textColor="@color/light_blue"

       />

   <ScrollView

        android:layout_width="match_parent"

        android:layout_height="160dp">

       <TextView

           android:id="@+id/status_view_a"

           android:layout_width="match_parent"

           android:layout_height="match_parent"

           android:background="@color/white"

           android:textColor="@color/black"

           android:padding="4dip"

           android:typeface="monospace"

           />

   </ScrollView>

   <TextView

       android:layout_width="match_parent"

       android:layout_height="wrap_content"

       android:textSize="@dimen/font_medium"

       android:text="@string/activity_status"

       android:textColor="@color/light_blue"

       />

   <TextView

       android:id="@+id/status_view_all_a"

       android:layout_width="match_parent"

       android:layout_height="wrap_content"

       android:background="@color/white"

       android:textColor="@color/black"

       android:padding="4dip"

       android:typeface="monospace"

       />

</LinearLayout>

AndroidMenifest.xml

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

   package="com.example.activitylifecycle"

   android:versionCode="1"

   android:versionName="1.0" >

   <uses-sdk

       android:minSdkVersion="8"

       android:targetSdkVersion="17" />

   <application

       android:allowBackup="true"

       android:icon="@drawable/ic_launcher"

       android:label="@string/app_name"

       android:theme="@style/AppTheme" >

       <activity

           android:name=".ActivityA"

           android:label="@string/app_name" >

           <intent-filter>

               <action android:name="android.intent.action.MAIN" />

               <category android:name="android.intent.category.LAUNCHER" />

           </intent-filter>

       </activity>

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

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

       <activity android:name=".DialogActivity"

                 android:theme="@android:style/Theme.Dialog">

       </activity>

       

   </application>

</manifest>