レイアウトでFragmentを使ったときにハマった話
activityだけだとなんか面白くなかったから「Fragmentも使ってみよう！」なんて調子に乗ったらハマってしまった・・・今回はそんなお話
Fragmentは簡単だけど、Android Studioさんが優秀でimportが統一できない！
Fragmentを使うときに止まった一番の原因はAlt+Enterでimportできる機能！
最近触り始めたということもあり、ショートカットを多いに使っているのですが、このショートカットの場合はとりあえず見つけたやつがimportに追加されるので全体のバージョンが統一できないのが問題だった。
とりあえず、AppCompatActivityがいけない。Activityをextendsしよう
extendsで継承できるのがAppcompatActivityだとimportが
- android.support.v7.app.AppCompatActivity
- android.support.v4.app.AppCompatActivity
になるから
- android.app.Activity
こっちをimportしてどうにか解決。
下記はそのソースコードになります。
MainActivity.java
package com.example.chibadai.myapp;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// コードからFragmentを追加
// Fragmentを作成
MainFragment fragment = new MainFragment();
// \fragmentの追加や削除といった変更を行う際は、Transactionを利用する
FragmentTransaction transaction = getFragmentManager().beginTransaction();
// 新しく追加を行うのでaddを使用
// ほかも、よく使う操作で、replace removeといったメソッドがある
// メソッドの１つ目の引数は対象のViewGroupのID、２つ目の引数は追加するfragment
transaction.add(R.id.container, fragment);
// 最後にcommitを使用することで変更を反映する
transaction.commit();
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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=".MainActivity">
<LinearLayout
android:layout_width="368dp"
android:layout_height="495dp"
android:orientation="vertical"
android:id="@+id/container"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent">
</LinearLayout>
</android.support.constraint.ConstraintLayout>
MainFragment.java
package com.example.chibadai.myapp;
import android.app.Fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class MainFragment extends Fragment {
private TextView mTextView;
/**
* Called to have the fragment instantiate its user interface view.
* This is optional, and non-graphical fragments can return null (which
* is the default implementation). This will be called between
* {@link #onCreate(Bundle)} and {@link #onActivityCreated(Bundle)}.
* <p>
* <p>If you return a View from here, you will later be called in
* {@link #onDestroyView} when the view is being released.
*
* @param inflater The LayoutInflater object that can be used to inflate
* any views in the fragment,
* @param container If non-null, this is the parent view that the fragment's
* UI should be attached to. The fragment should not add the view itself,
* but this can be used to generate the LayoutParams of the view.
* @param savedInstanceState If non-null, this fragment is being re-constructed
* from a previous saved state as given here.
* @return Return the View for the fragment's UI, or null.
*/
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
// 先程のレイアウトをここでViewとして作成する
return inflater.inflate(R.layout.fragment_main, container, false);
}
/**
* Called immediately after {@link #onCreateView(LayoutInflater, ViewGroup, Bundle)}
* has returned, but before any saved state has been restored in to the view.
* This gives subclasses a chance to initialize themselves once
* they know their view hierarchy has been completely created. The fragment's
* view hierarchy is not however attached to its parent at this point.
*
* @param view The View returned by {@link #onCreateView(LayoutInflater, ViewGroup, Bundle)}.
* @param savedInstanceState If non-null, this fragment is being re-constructed
*/
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
// TextViewを紐づける
mTextView = (TextView) view.findViewById(R.id.textView);
// Buttonのクリックしたときの処理を書く
view.findViewById(R.id.button).setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
mTextView.setText(mTextView.getText() + "!");
}
});
}
}
fragment_main.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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=".MainActivity">
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello Fragment!"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.032" />
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="106dp"
android:text="!"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintHorizontal_bias="0.52"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.548" />
</android.support.constraint.ConstraintLayout>
＜参考ページ＞