Android學習（三）fragment

fragment

fragment稱爲碎片，提供了重用性，減少了activity的代碼量。

fragment基本使用

使用流程基本和activity一致

1. 創建佈局文件，新建fragment類

創建佈局文件

<?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"
    android:background="@color/colorAccent">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:text="fragment content"/>

</LinearLayout>

新建TestFragment基礎Fragment，重寫onCreateView()方法

package com.example.testapplication;

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;

public class TestFragment extends Fragment {

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

2. 在Activity中添加進去
   創建Activity佈局文件

<?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"
    android:orientation="horizontal"
    tools:context="com.example.testapplication.ThirdActivity">
    
    <Button
        android:id="@+id/replace"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="replace"
        android:textAllCaps="false" />

    <LinearLayout
        android:id="@+id/test_fragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:orientation="vertical">

    </LinearLayout>
</LinearLayout>

這裏添加使用按鈕進行fragment替換的功能，代碼如下

package com.example.testapplication;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class ThirdActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_third);
        replaceFragment(new TestFragment());
        Button button = findViewById(R.id.replace);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                replaceFragment(new AnotherFragment());
            }
        });
    }

    private void replaceFragment(Fragment fragment) {
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.test_fragment, fragment);
        fragmentTransaction.commit();
    }
}

碎片的生命週期

碎片的狀態

1. 運行狀態
2. 暫停狀態
3. 停止狀態
4. 銷燬狀態

生命週期圖