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How to switch between Activities in Android

Android Develop ConnorFegan9284 51℃ 0评论

In Android user interface is displayed through an activity. In Android app development you might face situations where you need to switch between one Activity (Screen/View) to another. In this tutorial I will be discussing about switching between one Activity to another and sending data between activities.

How to switch between Activities in Android

Before getting into complete tutorial I am giving the code snippets for handling activities. Lets assume that our new Activity class name is SecondScreen.java

How to switch between Activities in Android

Opening new Activity

To open new activity following startActivity() or startActivityForResult() method will be used.

 Intent i = new Intent(getApplicationContext(), SecondScreen.class); StartActivity(i); 

 

Sending parameters to new Activity

To send parameter to newly created activity putExtra() methos will be used.

 i.putExtra("key", "value");  // Example of sending email to next screen as // Key = 'email' // value = 'myemail@gmail.com' i.putExtra("email", "myemail@gmail.com"); 

 

Receiving parameters on new Activity

To receive parameters on newly created activity getStringExtra() method will be used.

 Intent i = getIntent(); i.getStringExtra("key");  // Example of receiving parameter having key value as 'email' // and storing the value in a variable named myemail String myemail = i.getStringExtra("email"); 

 

Opening new Activity and expecting result

In some situations you might expect some data back from newly created activity. In that situations startActivityForResult() method is useful. And once new activity is closed you should you use onActivityResult() method to read the returned result.

 Intent i = new Intent(getApplicationContext(), SecondScreen.class); startActivityForResult(i, 100); // 100 is some code to identify the returning result  // Function to read the result from newly created activity @Override     protected void onActivityResult(int requestCode,                                      int resultCode, Intent data) {      super.onActivityResult(requestCode, resultCode, data);         if(resultCode == 100){               // Storing result in a variable called myvar              // get("website") 'website' is the key value result data           String mywebsite = data.getExtras().get("result");         }      } 

 

Sending result back to old activity when StartActivityForResult() is used

 Intent i = new Intent(); // Sending param key as 'website' and value as 'androidhive.info' i.putExtra("website", "AndroidHive.info");  // Setting resultCode to 100 to identify on old activity setResult(100,in); 

 

Closing Activity

To close activity call finish() method

 finish(); 

 

Add entry in AndroidManifest.xml

To run our application you should enter your new activity in AndroidManifest.xml file. Add new activity between <application> tags

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

 

Let’s Start with a simple project

So now we have all the code snippets related to activities. In this tutorial i created two xml layouts(screen1.xml, screen2.xml) and two Acvities(FirstScreenActivity.java, SecondScreenActivity.java). The following diagram will give you an idea about the file structure you will be need in this tutorial.

How to switch between Activities in Android

Now lets start by creating a simple project.

1. Create a new project File -> Android Project. While creating a new project give activity name as FirstScreenActivity.
2. Now you need to create user interface for the FirstScreenActivity.java
3. Create a new xml file in layout folder or rename the main.xml to screen1.xml
Right Click on Layout -> New -> Android XML file and name it as screen1.xml
4. Now insert the following code in screen1.xml to design a small layout. This layout contains simple form with a button.

 <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     android:orientation="vertical"     android:layout_width="fill_parent"     android:layout_height="fill_parent"     >     <TextView android:layout_width="fill_parent"       android:layout_height="wrap_content"       android:text="Name: "/>     <EditText android:id="@+id/name"       android:layout_width="fill_parent"       android:layout_height="wrap_content"       android:layout_marginBottom="10dip"/>     <TextView      android:layout_width="fill_parent"      android:layout_height="wrap_content"      android:text="Email: "      />     <EditText android:id="@+id/email"       android:layout_width="fill_parent"       android:layout_height="wrap_content"       android:layout_marginBottom="10dip"/>     <Button android:id="@+id/btnNextScreen"        android:layout_width="fill_parent"       android:layout_height="wrap_content"       android:text="Send to Next Screen"       android:layout_marginTop="15dip"/> </LinearLayout>  
How to switch between Activities in Android

5. Now open your FirstScreenActivity.java and Type the following code. In the following code we are creating a new Intent and passing parameters on clicking button.

 package com.example.androidswitchviews;  import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.Button; import android.widget.EditText;  public class FirstScreenActivity extends Activity {  // Initializing variables  EditText inputName;  EditText inputEmail;  @Override  public void onCreate(Bundle savedInstanceState) {   super.onCreate(savedInstanceState);   setContentView(R.layout.screen1);    inputName = (EditText) findViewById(R.id.name);   inputEmail = (EditText) findViewById(R.id.email);   Button btnNextScreen = (Button) findViewById(R.id.btnNextScreen);    //Listening to button event   btnNextScreen.setOnClickListener(new View.OnClickListener() {     public void onClick(View arg0) {     //Starting a new Intent     Intent nextScreen = new Intent(getApplicationContext(), SecondScreenActivity.class);      //Sending data to another Activity     nextScreen.putExtra("name", inputName.getText().toString());     nextScreen.putExtra("email", inputEmail.getText().toString());      Log.e("n", inputName.getText()+"."+ inputEmail.getText());      startActivity(nextScreen);     }   });  } } 

6. Create a class called SecondScreenActivity.java. Right Click on src/yourpackagefolder -> New -> Class and name it as SecondScreenActivity.java

How to switch between Activities in Android

7. Now we need interface for our Second Actvity. Create a new xml file and name it as screen2.xml.
Right Click on Layout -> New -> Android XML file and name it as screen2.xml. Insert the following code in screen2.xml.

 <?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">    <TextView android:layout_width="fill_parent"      android:layout_height="wrap_content"      android:text="You Entered..."      android:textSize="25dip"      android:gravity="center"      android:layout_margin="15dip"/>    <TextView android:id="@+id/txtName"      android:layout_width="fill_parent"      android:layout_height="wrap_content"      android:layout_margin="15dip"      android:textSize="18dip"/>    <TextView android:id="@+id/txtEmail"      android:layout_width="fill_parent"      android:layout_height="wrap_content"      android:layout_margin="15dip"      android:textSize="18dip"/>    <Button android:id="@+id/btnClose"      android:layout_width="fill_parent"      android:layout_height="wrap_content"      android:layout_marginTop="15dip"      android:text="Close"/>  </LinearLayout>  

8. Now open SecondScreenActivity.java and type the following code. Here we are simply reading the parameters and displaying them on to screen

 i.putExtra("key", "value");  // Example of sending email to next screen as // Key = 'email' // value = 'myemail@gmail.com' i.putExtra("email", "myemail@gmail.com"); 

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9. Now everything is ready and before running your project make sure that you an entry of new activity name in AndroidManifest.xml file. Open you AndroidManifest.xml file and modify the code as below

 i.putExtra("key", "value");  // Example of sending email to next screen as // Key = 'email' // value = 'myemail@gmail.com' i.putExtra("email", "myemail@gmail.com"); 

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10. Finally run your project by right clicking on your project folder -> Run As -> 1 Android Application. You can see the application is running by switching between screens. The below image is output screenshots of both xml files.

How to switch between Activities in Android

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