全局Context

全局Context

在许多方法执行的时候，都需要context做为参数。当你自己封装工具类等很多时候，你会获取不到，怎么办？全局Context解决了上述问题。

实现

新建MyApplication类继承Application，单例模式实现globalcontext。
修改AndroidManifest.xml文件中application标签的android:name属性。
调用

BLApplication.getContext();

示例代码

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BLApplication.java

public class BLApplication extends Application {

    private static Context sContext;

    @Override
    public void onCreate() {
        sContext = getApplicationContext();
    }

    public static Context getContext() {
        return sContext;
    }

    public static void initialize(Context context) {
        if (context != null) {
            sContext = context;
        }
    }
}

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AndroidManifest.xml

<application
        android:name=".chapter13.BLApplication"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme.NoActionBar">
</application>

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activity_global_context.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".chapter13.GlobalContextActivity">

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <Button
                android:id="@+id/btn_gc_1"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="使用全局context的Toast" />

        </LinearLayout>
    </ScrollView>

</LinearLayout>

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GlobalContextActivity.java

public class GlobalContextActivity extends MyBaseActivity {

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

        Button btn_gc_1 = findViewById(R.id.btn_gc_1);
        btn_gc_1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(BLApplication.getContext(),
                        "This is Toast used GolbalContext", Toast.LENGTH_LONG).show();
            }
        });

    }
}

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