Android-在Java布局内插入布局

Question

im begginer in android programming and i dont understand much how views and inflatting work. this is what i want to do: i want to have one main layout that includes another layout. this "another" layout i want to programmically change in java and in main activity to include it in main layout.

i have activity_main.xml

    <?xml version="1.0" encoding="utf-8"?>
    <android.support.design.widget.CoordinatorLayout 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="blahblah.MainActivity">

        <android.support.design.widget.AppBarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:theme="@style/AppTheme.AppBarOverlay">

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:background="?attr/colorPrimary"
                app:popupTheme="@style/AppTheme.PopupOverlay" />



        </android.support.design.widget.AppBarLayout>

        <LinearLayout

<!--here i want to include another layout-->
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:id="@+id/main_content"
            android:orientation="horizontal"></LinearLayout>

        <!--
            <include layout="@layout/content_main" />
        -->

    </android.support.design.widget.CoordinatorLayout>

inside linear layout main_content i want to include kalendar_view.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:id="@+id/textView11"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="TextView" />

    <Button
        android:id="@+id/button2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Button" />
</LinearLayout>

and this is my MainActivity.java

public class MainActivity extends AppCompatActivity {

    TextView tv;
    LinearLayout mainContent;
    KalendarView kv;
    Context context;
    LayoutInflater inflater;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        inflater=getLayoutInflater();
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        mainContent=(LinearLayout) findViewById(R.id.main_content);
        kv = new KalendarView(context, inflater);//this view i want to include in main layout
        mainContent.addView(kv);//trying to include
        setSupportActionBar(toolbar);
        tv= (TextView) findViewById(R.id.textView11);
    }
(...)

and KalendarView.java

  public class KalendarView extends LinearLayout {

       // LayoutInflater inflater;

        public KalendarView(Context context, LayoutInflater inflater){
            super(context);
           // inflater = (LayoutInflater)context.getSystemService
           //         (Context.LAYOUT_INFLATER_SERVICE);
            inflater.inflate(R.layout.kalendar_view, null);//trying to inflate
        }
//(...) some methods to programically change layout
    }

this app crashes, and i dont know why. my goal is to have more than one different instances of KalendarView class so that i can programically show one of them.

can someone explain me what is wrong with my code, and how to correctly include one layout inside another?

Answer 1

Your KalendarView shouldn't have an inflator as a parameter, and definitely shouldn't try to inflate itself. Your Kalendar view should look something like this:

  public class KalendarView extends LinearLayout {
        public KalendarView(Context context){
            super(context);
        }
//(...) some methods to programically change layout
    }

This is enough to be able to instantianate a view. IN your Main Activity you forgot to instantaniate your mainContent. It should look something like this:

public class MainActivity extends AppCompatActivity {

TextView tv;
LinearLayout mainContent;
KalendarView kv;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mainContent = (LinearLayout) findViewById(R.id.main_content);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    kv = new KalendarView(MainActivity.this);
    mainContent.addView(kv);
    setSupportActionBar(toolbar);
    tv= (TextView) findViewById(R.id.textView11);
}

(...)

Answer 2

The thing is, you need to attach it to root, like this

private void initView() {
    LayoutInflater.from(getContext()).inflate(R.layout.kalendar_view, this, true);
}

So your class should look like this:

public class KalendarView extends LinearLayout {

public KalendarView(Context context) {
    this(context, null);
}

public KalendarView(Context context,
                     @Nullable AttributeSet attrs) {
    super(context, attrs);
    initView();
}

public KalendarView(Context context,
                     @Nullable AttributeSet attrs,
                     int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    initView();
}

private void initView() {
    LayoutInflater.from(getContext()).inflate(R.layout.kalendar_view, this, true);
}
}