Android：加载fragment的两种方法

一、使用布局文件

LeftFragment

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.tencent.formalandroid.R;

public class LeftFragment extends Fragment {

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.left_fragment_layout, container, false);
        return view;
    }

    @Nullable
    @Override
    public View getView() {
        return super.getView();
    }
}

left_fragment_layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/left_fragment_text"/>

</LinearLayout>

activity_third.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">

    <fragment
        <!--注意：这里一定要设置id-->
        android:id="@+id/left_fragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:name="com.tencent.formalandroid.activity.LeftFragment"
        android:layout_weight="1"/>

    <fragment
        android:id="@+id/right_fragment"
        android:name="com.tencent.formalandroid.activity.RightFragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1" />

</LinearLayout>

ThirdActivity

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;

import com.tencent.formalandroid.R;

// 注意：这里一定不要用Activity，否则会闪退
public class ThirdActivity extends AppCompatActivity {

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

    }
}

---

二、通过Java Code

FourthActivity

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;

import com.tencent.formalandroid.R;

public class FourthActivity extends AppCompatActivity {

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

        FragmentManager manager = getSupportFragmentManager();
        FragmentTransaction transaction = manager.beginTransaction();

        LeftFragment leftFragment = new LeftFragment();
        transaction.add(R.id.container_for_fragment, leftFragment).commit();
    }
}

activity_fourth.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"
    android:background="@color/colorRed">

    <RelativeLayout
        android:id="@+id/container_for_fragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

注：LeftFragment同上。