关于DialogFragment的一些学习

标签（空格分隔）： DialogFrgment

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经历了一个月的项目期，Google给我的最好礼物莫过于谷歌官方网站了
点击进入Google官网DialogFragment介绍

自从Fragment时代的到来，任何View都可以封装到一个Fragment中，然后代替原来的固定的布局模式；DialogFragment因为继承于Fragment并封装了一个Dialog, 所以，有两种方式可以启动DialogFragment.

调用DialogFragment的show()方法，覆盖模式

void showDialog() {    // Create the fragment and show it as a dialog.    DialogFragment newFragment = MyDialogFragment.newInstance();    newFragment.show(getFragmentManager(), "dialog");}

show方法的实现

    public void show(FragmentManager manager, String tag) {        mDismissed = false;        mShownByMe = true;        FragmentTransaction ft = manager.beginTransaction();        ft.add(this, tag);        ft.commit();    }

按照Fragment的加载方式，加载到内容区域

FragmentTransaction ft = getFragmentManager().beginTransaction();DialogFragment newFragment = MyDialogFragment.newInstance();ft.add(R.id.embedded, newFragment);ft.commit();

在Dialog的构造方法中，实例化了一个属于自己的Window对象，这个很重要。

 Dialog(Context context, int theme, boolean createContextThemeWrapper) {  ····        mWindowManager = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);        Window w = PolicyManager.makeNewWindow(mContext);        mWindow = w;        w.setCallback(this);        w.setOnWindowDismissedCallback(this);        w.setWindowManager(mWindowManager, null, null);        w.setGravity(Gravity.CENTER);        mListenersHandler = new ListenersHandler(this);    }

public class Dialog implements DialogInterface, Window.Callback,        KeyEvent.Callback, OnCreateContextMenuListener, Window.OnWindowDismissedCallback {}

上面这段代码，表明Dialog能够接受Window的Callback，消失事件，按键事件（优先于宿主Activity）

这表明Dialog可以做很多事情，因为它拥有属于自己的Window，能够监听按键的事件，大家都有各种方式让Fragment变相监听到返回键。如何只需要一个页面的话，也可以考虑DialogFragment。
Demo: 设置Window的大小

Window window = getDialog().getWindow();        DisplayMetrics dm = new DisplayMetrics();        getActivity().getWindowManager().getDefaultDisplay().getMetrics(dm);        getDialog().getWindow().setLayout(dm.widthPixels,                getDialog().getWindow().getAttributes().height);        window.setBackgroundDrawable(new ColorDrawable(0xff000000));        WindowManager.LayoutParams layoutParams = window.getAttributes();        // 底部显示        layoutParams.gravity = Gravity.BOTTOM;        layoutParams.height = WindowManager.LayoutParams.MATCH_PARENT;        layoutParams.windowAnimations = com.jiuyuhulian.LiveRoom.R.style.BottomToTopAnim;        window.setAttributes(layoutParams);

DialogFragment实现的接口方法。

public void onCancel(DialogInterface dialog) {    }public void onDismiss(DialogInterface dialog) {    if (!mViewDestroyed) {        // Note: we need to use allowStateLoss, because the dialog        // dispatches this asynchronously so we can receive the call        // after the activity is paused.  Worst case, when the user comes        // back to the activity they see the dialog again.        dismissInternal(true);    }}

对比, 简单的解释就是，当我们锁屏的时候，我们的Dialog会调用dismissAllowingStateLoss(), 当解锁时，DialogFragment会再次显示出来，而dissmiss则会不保存这个状态。

public void dismiss() {        dismissInternal(false);    }public void dismissAllowingStateLoss() {        dismissInternal(true);    }

dismissInternal(boolean allowStateLoss)

void dismissInternal(boolean allowStateLoss) {        if (mDismissed) {            return;        }        mDismissed = true;        mShownByMe = false;        if (mDialog != null) {            mDialog.dismiss();            mDialog = null;        }        mViewDestroyed = true;        if (mBackStackId >= 0) {            getFragmentManager().popBackStack(mBackStackId,                    FragmentManager.POP_BACK_STACK_INCLUSIVE);            mBackStackId = -1;        } else {            FragmentTransaction ft = getFragmentManager().beginTransaction();            ft.remove(this);            if (allowStateLoss) {                ft.commitAllowingStateLoss();            } else {                ft.commit();            }        }    }

    @Override    public FragmentTransaction beginTransaction() {        return new BackStackRecord(this);    }

监听返回键

getDialog().setOnKeyListener(new DialogInterface.OnKeyListener() {            @Override            public boolean onKey(DialogInterface dialogInterface, int i, KeyEvent keyEvent) {                // 这里会优先监听到Key事件，最主要的是back键，注意back键有down和up事件                return false;            }        });

设置要在getLayoutInflater()方法之前，也就是在页面初始化之前

public void setStyle(int style, int theme) {        mStyle = style;        if (mStyle == STYLE_NO_FRAME || mStyle == STYLE_NO_INPUT) {            mTheme = com.android.internal.R.style.Theme_DeviceDefault_Dialog_NoFrame;        }        if (theme != 0) {            mTheme = theme;        }    }    public static final int STYLE_NO_TITLE = 1; // 没标题    public static final int STYLE_NO_FRAME = 2; // 无框的（没有层级）    public static final int STYLE_NO_INPUT = 3; // 不可输入