相信很多小夥伴們在使用Fragment都會遇到狀態儲存的問題，今天介紹一個簡單的案例。

大家都知道在使用Activity之間傳遞資料時大部分情況下都是用Bundle；

先幫大家複習一下Bundle，利用鍵值對(key-value)來儲存資料的，內部包含ArrayMap<String, Object> mMap = null;

1. 新建一個Bundle類：

Bundle mBundle = new Bundle();

2. Bundle可以儲存的資料型別：

mBundle.putInt("key1", 1);
mBundle.putString("key2", "測試");
mBundle.putParcelable("key3", user);
 

基本資料型別和物件資料型別【user implements Parcelable】

3. Activity傳遞資料：

Intent mIntent = new Intent(this, MnScaleBarActivity.class);
mIntent.putExtra("data", mBundle);
startActivity(mIntent);

Ok，現在來說說Fragment與Bundle

在Fragment中有兩個方法：

/**
     * Supply the construction arguments for this fragment.  This can only
     * be called before the fragment has been attached to its activity; that
     * is, you should call it immediately after constructing the fragment.  The
     * arguments supplied here will be retained across fragment destroy and
     * creation.
     */
    public void setArguments(Bundle args) {
        if (mIndex >= 0) {
            throw new IllegalStateException("Fragment already active");
        }
        mArguments = args;
    }

    /**
     * Return the arguments supplied when the fragment was instantiated,
     * if any.
     */
    final public Bundle getArguments() {
        return mArguments;
    }
 

1. 在Fragment的子類呼叫getArguments()獲取Bundle物件，獲取物件如果為null可以新建Bundle呼叫setArguments()重新設定

2. 新建Fragment子類StateFragment

public class StateFragment extends Fragment{

    private Bundle saveState;

    private String tag = StateFragment.class.getSimpleName();

    public StateFragment(){
        super();
        if(getArguments() == null){
            setArguments(new Bundle());
        }
    }
}
 

3. 子類重寫父類方法onSaveInstanceState()和OnDestoryView()進行儲存資料：

@Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        saveStateToArguments();
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        saveStateToArguments();
    }

4. 儲存狀態saveStateToArguments()

private void saveStateToArguments(){
        if(getView() != null){
            saveState = saveState();
        }
        if(saveState != null){
            Bundle b = getArguments();
            if(b!=null){
                b.putBundle("internalSavedViewState8954201239547", saveState);
            }
        }
    }

4.1 供子類呼叫的狀態儲存方法

/**
     * 儲存狀態
     * */
    private Bundle saveState(){
        Bundle state = new Bundle();
        //儲存資料
        onSaveState(state);
        return state;
    }

    /**
     * 子類重寫該方法實現狀態儲存
     * */
    public void onSaveState(Bundle outState){

    }

5. 恢復狀態restoreStateArguments()

private boolean restoreStateFromArguments(){
        Bundle b = getArguments();
        if(b == null) return false;
        saveState = b.getBundle("internalSavedViewState8954201239547");
        if(saveState != null){
            restoreState();
            return true;
        }
        return false;
    }

5.1 供子類恢復狀態的方法

/**
     * 恢復狀態
     * */
    private void restoreState(){
        if(saveState != null){
            onRestoreState(saveState);
        }
    }

    /**
     * 子類重寫該方法恢復狀態
     * */
    public void onRestoreState(Bundle saveInstanceState){

    }

原始碼如下：

package cc.mntabdemo;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * User: 山野書生([email protected])
 * Date: 2015-11-27
 * Time: 15:21
 * Version 1.0
 */

public class StateFragment extends Fragment{

    private Bundle saveState;

    private String tag = StateFragment.class.getSimpleName();

    public StateFragment(){
        super();
        if(getArguments() == null){
            setArguments(new Bundle());
        }
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        if(!restoreStateFromArguments()){
            onFirstTimeLaunched();
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return super.onCreateView(inflater, container, savedInstanceState);
    }

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

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        saveStateToArguments();
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        saveStateToArguments();
    }

    /**
     * 第一次載入該類
     * */
    public void onFirstTimeLaunched(){

    }

    private void saveStateToArguments(){
        if(getView() != null){
            saveState = saveState();
        }
        if(saveState != null){
            Bundle b = getArguments();
            if(b!=null){
                b.putBundle("internalSavedViewState8954201239547", saveState);
            }
        }
    }

    private boolean restoreStateFromArguments(){
        Bundle b = getArguments();
        if(b == null) return false;
        saveState = b.getBundle("internalSavedViewState8954201239547");
        if(saveState != null){
            restoreState();
            return true;
        }
        return false;
    }

    /**
     * 恢復狀態
     * */
    private void restoreState(){
        if(saveState != null){
            onRestoreState(saveState);
        }
    }

    /**
     * 子類重寫該方法恢復狀態
     * */
    public void onRestoreState(Bundle saveInstanceState){

    }

    /**
     * 儲存狀態
     * */
    private Bundle saveState(){
        Bundle state = new Bundle();
        //儲存資料
        onSaveState(state);
        return state;
    }

    /**
     * 子類重寫該方法實現狀態儲存
     * */
    public void onSaveState(Bundle outState){

    }

}

子類：

package cc.mntabdemo;

import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RelativeLayout;
import android.widget.TextView;

/**
 * User: 山野書生([email protected])
 * Date: 2015-11-26
 * Time: 16:26
 * Version 1.0
 */

public class ContentFragment extends StateFragment {

    private TextView text;
    private Button btn;
    private EditText edit;

    private String mTitle;

    private String tag = ContentFragment.class.getSimpleName();

    public ContentFragment(){
        super();
    }

    public ContentFragment(String title){
        super();
        mTitle = title;
    }

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

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        initViews(view);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                text.setText(edit.getText().toString());
            }
        });
    }

    private void initViews(View view){
        text = (TextView)view.findViewById(R.id.text);
        btn = (Button)view.findViewById(R.id.btn);
        edit = (EditText)view.findViewById(R.id.edit);
    }

    @Override
    public void onRestoreState(Bundle saveInstanceState) {
        edit.setText(saveInstanceState.getString("edit"));
        text.setText(saveInstanceState.getString("text"));
    }

    @Override
    public void onSaveState(Bundle outState) {
        outState.putString("edit", edit.getText().toString());
        outState.putString("text", text.getText().toString());
    }
}

佈局程式碼：

<?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"
    >

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/edit"
        />

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

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/text"
        />

</LinearLayout>

EditText自身可以儲存以及恢復

本專案原始碼：原始碼
本Demo在MnTabDemo基礎上完成，包含【高仿微信6.0底部Tab和StatedFragment】；

高仿微信6.0底部Tab在另一個教程講解