android开发之Fragment利用Bundle保存状态

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相信很多小伙伴们在使用Fragment都会遇到状态保存的问题，今天介绍一个简单的案例。

大家都知道在使用Activity之间传递数据时大部分情况下都是用Bundle；

先帮大家复习一下Bundle，利用键值对(key-value)来存储数据的，内部包含ArrayMap<String, Object> mMap = null;

1. 新建一个Bundle类：

Bundle mBundle = new Bundle();

2. Bundle可以储存的数据类型：

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

基本数据类型和对象数据类型【user implements Parcelable】

3. Activity传递数据：

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

Ok，现在来说说Fragment与Bundle

在Fragment中有两个方法：

/**     * 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的子类调用getArguments()获取Bundle对象，获取对象如果为null可以新建Bundle调用setArguments()重新设置

2. 新建Fragment子类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. 子类重写父类方法onSaveInstanceState()和OnDestoryView()进行保存数据：

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

4. 保存状态saveStateToArguments()

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

4.1 供子类调用的状态保存方法

/**     * 保存状态     * */    private Bundle saveState(){        Bundle state = new Bundle();        //保存数据        onSaveState(state);        return state;    }    /**     * 子类重写该方法实现状态保存     * */    public void onSaveState(Bundle outState){    }

5. 恢复状态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 供子类恢复状态的方法

/**     * 恢复状态     * */    private void restoreState(){        if(saveState != null){            onRestoreState(saveState);        }    }    /**     * 子类重写该方法恢复状态     * */    public void onRestoreState(Bundle saveInstanceState){    }

源码如下：

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: 山野书生(1203596603@qq.com) * 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();    }    /**     * 第一次加载该类     * */    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;    }    /**     * 恢复状态     * */    private void restoreState(){        if(saveState != null){            onRestoreState(saveState);        }    }    /**     * 子类重写该方法恢复状态     * */    public void onRestoreState(Bundle saveInstanceState){    }    /**     * 保存状态     * */    private Bundle saveState(){        Bundle state = new Bundle();        //保存数据        onSaveState(state);        return state;    }    /**     * 子类重写该方法实现状态保存     * */    public void onSaveState(Bundle outState){    }}

子类：

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: 山野书生(1203596603@qq.com) * 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());    }}

布局代码：

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

EditText自身可以保存以及恢复

感谢开源项目：StatedFragment

本项目源码：源码
本Demo在MnTabDemo基础上完成，包含【高仿微信6.0底部Tab和StatedFragment】；

高仿微信6.0底部Tab在另一个教程讲解

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