java 从另一个活动中获取变量（Android Studio）

Get Variable from another Activity (Android Studio)

提问by tobekingforaday

I know that there are a lot of answers to this question already, but I'm still having trouble dealing with this concept.

我知道这个问题已经有很多答案，但我仍然无法处理这个概念。

An answer found hereshows:

此处找到的答案显示：

If you didn't want to use a global variable you could always create a method in your activity to return your string.

如果您不想使用全局变量，您始终可以在您的活动中创建一个方法来返回您的字符串。

    public String getMyString(){
         return item; } 

Then in your current activity you could call:

然后在您当前的活动中，您可以调用：

    String myValue = LoginScreen.getMyString();

When I try this method, I am returned an error saying "Non-Static method can not be referenced from a static context". However if I make the methodstatic it says that my variableneeds to be static, but I need to update the variable. I'll include my code below.

当我尝试此方法时，返回一个错误消息，提示“无法从静态上下文中引用非静态方法”。但是，如果我将方法设为静态，则表示我的变量需要是静态的，但我需要更新变量。我将在下面包含我的代码。

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First Activity -

第一个活动 -

btnSEARCH.setOnClickListener(new View.OnClickListener() {
    public void onClick(View view) {
        if (editTextSearch.getText().toString() != null) {
            SearchQueryTerm = editTextSearch.getText().toString();
            editTextSearch.setText("");
        }
    }
});

public String getMyString(){
    return SearchQueryTerm;
}

Second Activity-

第二个活动-

String SearchQueryTerm = MainActivity.getMyString();

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I truly appreciate any help you can give me in this. Thanks so much!! <3

我真的很感激你能在这方面给我的任何帮助。非常感谢！！<3

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This is my updated code - however it still crashes :(

这是我更新的代码 - 但是它仍然崩溃:(

Activity 1

活动一

public void sendMessageIntent(View view) {
    Intent search_intent = new Intent(this, SearchActivity.class);
    api_intent.putExtra("my_variable", SearchQueryTerm);
    startActivity(search_intent);
}

xml file

xml文件

 <Button
        android:id="@+id/button_view"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="right"
        android:text="View"
        android:onClick="sendMessageIntent"
        />

Activity 2 -

活动 2 -

public String SearchQueryTerm

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_enter_variable);

        if (extras != null) {
            SearchQueryTerm = extras.getString("my_variable");
        }
}

回答by Yassine.b

Use putExtra method of an object Intent.

使用对象 Intent 的 putExtra 方法。

In your first activity create for example :

在您的第一个活动中创建例如：

String value = "value";
Intent i = new Intent(getApplicationContext(), MyActivity.class);
i.putExtra("my_variable",value);
startActivity(i);

In your second activity you can retrieve your variable :

在您的第二个活动中，您可以检索您的变量：

Bundle extras = getIntent().getExtras();
if (extras != null) {
    String value = extras.getString("my_variable");
}

It's the best method to pass a variable between activities.

这是在活动之间传递变量的最佳方法。

---

---

To show you how it works, i have done this code :

为了向您展示它是如何工作的，我已经完成了以下代码：

XML of first activity :

第一个活动的 XML：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">
        <EditText
            android:id="@+id/editTextSearch"
            android:layout_width="200dp"
            android:layout_height="wrap_content" />

        <Button
            android:id="@+id/buttonSearch"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:text="Button"/>
    </LinearLayout>

</RelativeLayout>

First Activity :

第一个活动：

public class MainActivity extends AppCompatActivity {

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

        Button btnSEARCH = (Button) findViewById(R.id.buttonSearch);

        btnSEARCH.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                EditText editTextSearch = (EditText) findViewById(R.id.editTextSearch);
                if (editTextSearch.getText().toString() != null) {
                    String value = "value";
                    Intent i = new Intent(getApplicationContext(), Main2Activity.class);
                    i.putExtra("SearchQueryTerm",editTextSearch.getText().toString());
                    startActivity(i);
                    editTextSearch.setText("");
                }
            }
        });
    }

}

In this first activity we pass the value of the editText in the putExtra method with the key = "SearchQueryTerm".

在第一个活动中，我们使用键 = "SearchQueryTerm" 在 putExtra 方法中传递 editText 的值。

To retrieve the value of editText do this in your second Activity :

要检索 editText 的值，请在第二个 Activity 中执行此操作：

public class Main2Activity extends AppCompatActivity {

    String SearchQueryTerm = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

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

        System.out.println(SearchQueryTerm);
    }

}

Now you have the value of your editText in the variable SearchQueryTerm ( Second Activity ).

现在，您在变量 SearchQueryTerm ( Second Activity ) 中拥有了 editText 的值。

It works for me, so there is no reason it dont work for you.

它对我有用，所以没有理由对你不起作用。

Hope it helps.

希望能帮助到你。

回答by Jerome B.

a good solution is to add a "model" singleton class, where you store data that have to be shared between your activities

一个好的解决方案是添加一个“模型”单例类，您可以在其中存储必须在您的活动之间共享的数据

example :

例子 ：

public class Model {
private static Model __instance == null;

private Model() {
}

public static Model instance() {
    if (__instance == null) {
        __instance = new Model();
    }
    return __instance;
}

private Object mydataToShare = null;

public void setMyDataToShare(Object mydataToShare) {
    this.mydataToShare = mydataToShare; 
}

public Object getMyDataToShare() {
    return mydataToShare;
}

}

}

to store data :

存储数据：

Model.instance().setMyDataToShare(<value to store>);

to retrieve data :

检索数据：

Object valueToRetrieve = Model.instance().getMyDataToShare();

it allow you to transfer complex data and separate completely logic part from UI

它允许您传输复杂的数据并将逻辑部分与 UI 完全分离