In an Android applic开发者_如何学Pythonation, how do you start a new activity (GUI) when a button in another activity is clicked, and how do you pass data between these two activities?

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Easy.

Intent myIntent = new Intent(CurrentActivity.this, NextActivity.class);
myIntent.putExtra("key", value); //Optional parameters
CurrentActivity.this.startActivity(myIntent);

Extras are retrieved on the other side via:

@Override
protected void onCreate(Bundle savedInstanceState) {
    Intent intent = getIntent();
    String value = intent.getStringExtra("key"); //if it's a string you stored.
}

Don't forget to add your new activity in the AndroidManifest.xml:

<activity android:label="@string/app_name" android:name="NextActivity"/>

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Current responses are great but a more comprehensive answer is needed for beginners. There are 3 different ways to start a new activity in Android, and they all use the Intent class; Intent | Android Developers.

1. Using the onClick attribute of the Button. (Beginner)
2. Assigning an OnClickListener() via an anonymous class. (Intermediate)
3. Activity wide interface method using the switch statement. (not-"Pro")

Here's the link to my example if you want to follow along:

1. Using the onClick attribute of the Button. (Beginner)

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Buttons have an onClick attribute that is found within the .xml file:

<Button
    android:id="@+id/button1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="goToAnActivity"
    android:text="to an activity" />

<Button
    android:id="@+id/button2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="goToAnotherActivity"
    android:text="to another activity" />

In Java class:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main_activity);
}

public void goToAnActivity(View view) {
    Intent intent = new Intent(this, AnActivity.class);
    startActivity(intent);
}

public void goToAnotherActivity(View view) {
    Intent intent = new Intent(this, AnotherActivity.class);
    startActivity(intent);
}

Advantage: Easy to make on the fly, modular, and can easily set multiple onClicks to the same intent.

Disadvantage: Difficult readability when reviewing.

2. Assigning an OnClickListener() via an anonymous class. (Intermediate)

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This is when you set a separate setOnClickListener() to each button and override each onClick() with its own intent.

In Java class:

@Override
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_activity);

        Button button1 = (Button) findViewById(R.id.button1);
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(view.getContext(), AnActivity.class);
                view.getContext().startActivity(intent);}
            });

        Button button2 = (Button) findViewById(R.id.button2);
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(view.getContext(), AnotherActivity.class);
                view.getContext().startActivity(intent);}
            });

Advantage: Easy to make on the fly.

Disadvantage: There will be a lot of anonymous classes which will make readability difficult when reviewing.

3. Activity wide interface method using the switch statement. (not-"Pro")

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This is when you use a switch statement for your buttons within the onClick() method to manage all the Activity's buttons.

In Java class:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main_activity);

    Button button1 = (Button) findViewById(R.id.button1);
    Button button2 = (Button) findViewById(R.id.button2);
    button1.setOnClickListener(this);
    button2.setOnClickListener(this);
}

@Override
public void onClick(View view) {
    switch (view.getId()){
        case R.id.button1:
            Intent intent1 = new Intent(this, AnActivity.class);
            startActivity(intent1);
            break;
        case R.id.button2:
            Intent intent2 = new Intent(this, AnotherActivity.class);
            startActivity(intent2);
            break;
        default:
            break;
    }

Advantage: Easy button management because all button intents are registered in a single onClick() method

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For the second part of the question, passing data, please see How do I pass data between Activities in Android application?

Edit: not-"Pro"

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Create an intent to a ViewPerson activity and pass the PersonID (for a database lookup, for example).

Intent i = new Intent(getBaseContext(), ViewPerson.class);                      
i.putExtra("PersonID", personID);
startActivity(i);

Then in ViewPerson Activity, you can get the bundle of extra data, make sure it isn't null (in case if you sometimes don't pass data), then get the data.

Bundle extras = getIntent().getExtras();
if(extras !=null)
{
     personID = extras.getString("PersonID");
}

Now if you need to share data between two Activities, you can also have a Global Singleton.

public class YourApplication extends Application 
{     
     public SomeDataClass data = new SomeDataClass();
}

Then call it in any activity by:

YourApplication appState = ((YourApplication)this.getApplication());
appState.data.CallSomeFunctionHere(); // Do whatever you need to with data here.  Could be setter/getter or some other type of logic

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When user clicks on the button, directly inside the XML like that:

<Button
         android:id="@+id/button"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="TextButton"
         android:onClick="buttonClickFunction"/>

Using the attribute android:onClick we declare the method name that has to be present on the parent activity. So I have to create this method inside our activity like that:

public void buttonClickFunction(View v)
{
            Intent intent = new Intent(getApplicationContext(), Your_Next_Activity.class);
            startActivity(intent);
}

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Intent iinent= new Intent(Homeactivity.this,secondactivity.class);
startActivity(iinent);

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    Intent in = new Intent(getApplicationContext(),SecondaryScreen.class);    
    startActivity(in);

    This is an explicit intent to start secondscreen activity.

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Emmanuel,

I think the extra info should be put before starting the activity otherwise the data won't be available yet if you're accessing it in the onCreate method of NextActivity.

Intent myIntent = new Intent(CurrentActivity.this, NextActivity.class);

myIntent.putExtra("key", value);

CurrentActivity.this.startActivity(myIntent);

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Try this simple method.

startActivity(new Intent(MainActivity.this, SecondActivity.class));

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From the sending Activity try the following code

   //EXTRA_MESSAGE is our key and it's value is 'packagename.MESSAGE'
    public static final String EXTRA_MESSAGE = "packageName.MESSAGE";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
       ....

        //Here we declare our send button
        Button sendButton = (Button) findViewById(R.id.send_button);
        sendButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //declare our intent object which takes two parameters, the context and the new activity name

                // the name of the receiving activity is declared in the Intent Constructor
                Intent intent = new Intent(getApplicationContext(), NameOfReceivingActivity.class);

                String sendMessage = "hello world"
                //put the text inside the intent and send it to another Activity
                intent.putExtra(EXTRA_MESSAGE, sendMessage);
                //start the activity
                startActivity(intent);

            }

From the receiving Activity try the following code:

   protected void onCreate(Bundle savedInstanceState) {
 //use the getIntent()method to receive the data from another activity
 Intent intent = getIntent();

//extract the string, with the getStringExtra method
String message = intent.getStringExtra(NewActivityName.EXTRA_MESSAGE);

Then just add the following code to the AndroidManifest.xml file

  android:name="packagename.NameOfTheReceivingActivity"
  android:label="Title of the Activity"
  android:parentActivityName="packagename.NameOfSendingActivity"

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Intent i = new Intent(firstactivity.this, secondactivity.class);
startActivity(i);

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Kotlin

First Activity

startActivity(Intent(this, SecondActivity::class.java)
  .putExtra("key", "value"))

Second Activity

val value = getIntent().getStringExtra("key")

Suggestion

Always put keys in constant file for more managed way.

companion object {
    val PUT_EXTRA_USER = "user"
}
startActivity(Intent(this, SecondActivity::class.java)
  .putExtra(PUT_EXTRA_USER, "value"))

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Starting an activity from another activity is very common scenario among android applications.
To start an activity you need an Intent object.

How to create Intent Objects?

An intent object takes two parameter in its constructor

1. Context
2. Name of the activity to be started. (or full package name)

Example:

So for example,if you have two activities, say HomeActivity and DetailActivity and you want to start DetailActivity from HomeActivity (HomeActivity-->DetailActivity).

Here is the code snippet which shows how to start DetailActivity from

HomeActivity.

Intent i = new Intent(HomeActivity.this,DetailActivity.class);
startActivity(i);

And you are done.

Coming back to button click part.

Button button = (Button) findViewById(R.id.someid);

button.setOnClickListener(new View.OnClickListener() {
     
     @Override
     public void onClick(View view) {
         Intent i = new Intent(HomeActivity.this,DetailActivity.class);
         startActivity(i);  
      }

});

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The way to start new activities is to broadcast an intent, and there is a specific kind of intent that you can use to pass data from one activity to another. My recommendation is that you check out the Android developer docs related to intents; it's a wealth of info on the subject, and has examples too.

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You can try this code:

Intent myIntent = new Intent();
FirstActivity.this.SecondActivity(myIntent);

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Start another activity from this activity and u can pass parameters via Bundle Object also.

Intent intent = new Intent(getBaseContext(), YourActivity.class);
intent.putExtra("USER_NAME", "xyz@gmail.com");
startActivity(intent);

Retrive data in another activity (YourActivity)

String s = getIntent().getStringExtra("USER_NAME");

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// In Kotlin , you can do as /* In First Activity, let in activity layout there is button which has id as button. Suppose I have to pass data as String type from one activity to another */

     val btn = findViewById<Button>(R.id.button)
     btn.setOnClickListener {
        val intent = Intent(baseContext, SecondActivity::class.java).apply {
             putExtra("KEY", data)
        }
        startActivity(intent)
     }

// In Second Activity, you can get data from another activity as

 val name = intent.getStringExtra("KEY")

/* Suppose you have to pass a Custom Object then it should be Parcelable. let there is class Collage type which I have to pass from one activity to another */

import android.os.Parcelable
import kotlinx.android.parcel.Parcelize

@Parcelize
class Collage(val name: String, val mobile: String, val email: String) : Parcelable

/* Activity First , let here data is Collage type. which I have to pass to another activity. */

val btn = findViewById<Button>(R.id.button)
         btn.setOnClickListener {
            val intent = Intent(baseContext, SecondActivity::class.java).apply {
                 putExtra("KEY", data)
            }
            startActivity(intent)
         }

// then from second Activity we will get as

val item = intent.extras?.getParcelable<Collage>("KEY")

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Button button = findViewById(R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(SplashActivity.this,HomeActivity.class);
            startActivity(intent);
        }
    });

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Implement the View.OnClickListener interface and override the onClick method.

ImageView btnSearch;

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_search1);
        ImageView btnSearch = (ImageView) findViewById(R.id.btnSearch);
        btnSearch.setOnClickListener(this);
    }

@Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.btnSearch: {
                Intent intent = new Intent(Search.this,SearchFeedActivity.class);
                startActivity(intent);
                break;
            }

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Although proper answers have been already provided but I am here for searching the answer in language Kotlin. This Question is not about language specific so I am adding the code to accomplish this task in Kotlin language.

Here is how you do this in Kotlin for andorid

testActivityBtn1.setOnClickListener{
      val intent = Intent(applicationContext,MainActivity::class.java)
      startActivity(intent)

 }

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The Most simple way to open activity on button click is:

1. Create two activities under the res folder, add a button to the first activity and give a name to onclick function.
2. There should be two java files for each activity.
3. Below is the code:

MainActivity.java

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import android.content.Intent;
public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void goToAnotherActivity(View view) {
        Intent intent = new Intent(this, SecondActivity.class);
        startActivity(intent);
    }
}

SecondActivity.java

package com.example.myapplication;
import android.app.Activity;
import android.os.Bundle;
public class SecondActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity1);
    }
}

AndroidManifest.xml(Just add this block of code to the existing)

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

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Take Button in xml first.

  <Button
        android:id="@+id/pre"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@mipmap/ic_launcher"
        android:text="Your Text"
        />

Make listner of button.

 pre.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, SecondActivity.class);
            startActivity(intent);
        }
    });

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When button is clicked:

loginBtn.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        Intent intent= new Intent(getApplicationContext(), NextActivity.class);
        intent.putExtra("data", value); //pass data
        startActivity(intent);
    }
});

To received the extra data from NextActivity.class :

Bundle extra = getIntent().getExtras();
if (extra != null){
    String str = (String) extra.get("data"); // get a object
}

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Write the code in your first activity .

button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {


Intent intent = new Intent(MainActivity.this, SecondAcitvity.class);
                       //You can use String ,arraylist ,integer ,float and all data type.
                       intent.putExtra("Key","value");
                       startActivity(intent);
                        finish();
            }
         });

In secondActivity.class

String name = getIntent().getStringExtra("Key");

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Place button widget in xml like below

<Button
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Button"
/>

After that initialise and handle on click listener in Activity like below ..

In Activity On Create method :

Button button =(Button) findViewById(R.id.button); 
button.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
       Intent intent = new 
            Intent(CurrentActivity.this,DesiredActivity.class);
            startActivity(intent);
    }
});

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An old question but if the goal is to switch displayed pages, I just have one activity and call setContentView() when I want to switch pages (usually in response to user clicking on a button). This allows me to simply call from one page's contents to another. No Intent insanity of extras parcels bundles and whatever trying to pass data back and forth.

I make a bunch of pages in res/layout as usual but don't make an activity for each. Just use setContentView() to switch them as needed.

So my one-and-only onCreate() has:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    LayoutInflater layoutInflater = getLayoutInflater();

    final View mainPage = layoutInflater.inflate(R.layout.activity_main, null);
    setContentView (mainPage);
    Button openMenuButton = findViewById(R.id.openMenuButton);

    final View menuPage = layoutInflatter.inflate(R.layout.menu_page, null);
    Button someMenuButton = menuPage.findViewById(R.id.someMenuButton);

    openMenuButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            setContentView(menuPage);
        }
    });

    someMenuButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            do-something-interesting;
            setContentView(mainPage);
        }
    }
}

If you want the Back button to go back through your internal pages before exiting the app, just wrap setContentView() to save pages in a little Stack of pages, and pop those pages in onBackPressed() handler.

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your button xml:

 <Button
    android:id="@+id/btn"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="jump to activity b"
    />

Mainactivity.java:

 Button btn=findViewVyId(R.id.btn);
btn.setOnClickListener(btnclick);
btnclick.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
               Intent intent=new Intent();
                intent.setClass(Mainactivity.this,b.class);
                startActivity(intent);
    }
});

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 imageView.setOnClickListener(v -> {
// your code here
        });

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Kotlin 2022

The simplest way:

val a = Intent(this.context, BarcodeActivity::class.java)
        a.putExtra("barcode", barcode)
        startActivity(a)

and in the other side (BarcodeActivity in my case):

val intent: Intent = intent
var data = intent.getStringExtra("barcode")

Read more here