Android(安卓)开发笔记第二季 DialogFragment

public class MainActivity extends Activity implements View.OnClickListener {    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        findViewById(R.id.btn).setOnClickListener(this);        FragmentManager.enableDebugLogging(true);    }    @Override    public void onClick(View view) {        showDialog();    }    private void showDialog() {        new MyDialogFragment().show(getFragmentManager(), "Tag1");    }}

08-01 21:23:07.521 16125-16125/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Commit: android.app.BackStackRecord@41cf3ea0
08-01 21:23:07.521 16125-16125/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Run: android.app.BackStackRecord@41cf3ea0
08-01 21:23:07.521 16125-16125/com.androidbook.fragments.dialogs V/FragmentManager﹕ add: MyDialogFragment{41cf3dd8 Tag1}
08-01 21:23:07.521 16125-16125/com.androidbook.fragments.dialogs V/FragmentManager﹕ Allocated fragment index MyDialogFragment{41cf3dd8 #0 Tag1}
08-01 21:23:07.521 16125-16125/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto CREATED: MyDialogFragment{41cf3dd8 #0 Tag1}
08-01 21:23:07.526 16125-16125/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto ACTIVITY_CREATED: MyDialogFragment{41cf3dd8 #0 Tag1}
08-01 21:23:07.531 16125-16125/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto STARTED: MyDialogFragment{41cf3dd8 #0 Tag1}
08-01 21:23:07.541 16125-16125/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto RESUMED: MyDialogFragment{41cf3dd8 #0 Tag1}

这是显示 DF(DialogFragment) 时的日志。

提交事务，实质上是提交一条 BSR(BackStackRecord)，然后处理这条 BSR。

FM(FragmentManger) 开始 add DF 41cf3dd8(唯一标识) Tag1。

为该 DF 申请空间，然后经历了 DF 的4中生命周期。

08-01 21:31:56.551 16125-16125/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Commit: android.app.BackStackRecord@41cff170
08-01 21:31:56.566 16125-16125/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Run: android.app.BackStackRecord@41cff170
08-01 21:31:56.566 16125-16125/com.androidbook.fragments.dialogs V/FragmentManager﹕ remove: MyDialogFragment{41cf3dd8 #0 Tag1} nesting=0
08-01 21:31:56.566 16125-16125/com.androidbook.fragments.dialogs V/FragmentManager﹕ movefrom RESUMED: MyDialogFragment{41cf3dd8 #0 Tag1}
08-01 21:31:56.571 16125-16125/com.androidbook.fragments.dialogs V/FragmentManager﹕ movefrom STARTED: MyDialogFragment{41cf3dd8 #0 Tag1}
08-01 21:31:56.571 16125-16125/com.androidbook.fragments.dialogs V/FragmentManager﹕ movefrom ACTIVITY_CREATED: MyDialogFragment{41cf3dd8 #0 Tag1}
08-01 21:31:56.571 16125-16125/com.androidbook.fragments.dialogs V/FragmentManager﹕ movefrom CREATED: MyDialogFragment{41cf3dd8 #0 Tag1}
08-01 21:31:56.571 16125-16125/com.androidbook.fragments.dialogs V/FragmentManager﹕ Freeing fragment index MyDialogFragment{41cf3dd8 #0 Tag1}

这是 dismiss DF 时产生的日志，dismiss 和 hide 不同，是确实会释放资源的。

同样的，提交BSR，执行BSR，

FM 开始 remove DF 41cf3dd8 #0(位置) Tag1 nesting=0(没有关联，这个不管，我不用addBackStack的)，

与之前反向的顺序经历四个生命周期，最后释放资源。

这样的DF已经满足了基本的提示性质的 Dialog 了。

但对于遮罩Dialog 或那些有性能洁癖的人，应该尝试下面这种。

public class MainActivity extends Activity implements View.OnClickListener {    private DialogFragment dialogFragment = new DialogFragment();    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        findViewById(R.id.btn).setOnClickListener(this);        FragmentManager.enableDebugLogging(true);    }    @Override    public void onClick(View view) {        dialogFragment.show(getFragmentManager(), "Tag1");        dialogFragment.dismiss();    }}

08-01 21:40:19.081 18118-18118/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Commit: android.app.BackStackRecord@41ce3ea0
08-01 21:40:19.081 18118-18118/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Commit: android.app.BackStackRecord@41ce4290
08-01 21:40:19.081 18118-18118/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Run: android.app.BackStackRecord@41ce3ea0
08-01 21:40:19.086 18118-18118/com.androidbook.fragments.dialogs V/FragmentManager﹕ add: DialogFragment{41cc3a60 Tag1}
08-01 21:40:19.086 18118-18118/com.androidbook.fragments.dialogs V/FragmentManager﹕ Allocated fragment index DialogFragment{41cc3a60 #0 Tag1}
08-01 21:40:19.091 18118-18118/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto CREATED: DialogFragment{41cc3a60 #0 Tag1}
08-01 21:40:19.091 18118-18118/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto ACTIVITY_CREATED: DialogFragment{41cc3a60 #0 Tag1}
08-01 21:40:19.091 18118-18118/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto STARTED: DialogFragment{41cc3a60 #0 Tag1}
08-01 21:40:19.121 18118-18118/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto RESUMED: DialogFragment{41cc3a60 #0 Tag1}
08-01 21:40:19.121 18118-18118/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Run: android.app.BackStackRecord@41ce4290
08-01 21:40:19.121 18118-18118/com.androidbook.fragments.dialogs V/FragmentManager﹕ remove: DialogFragment{41cc3a60 #0 Tag1} nesting=0
08-01 21:40:19.121 18118-18118/com.androidbook.fragments.dialogs V/FragmentManager﹕ movefrom RESUMED: DialogFragment{41cc3a60 #0 Tag1}
08-01 21:40:19.121 18118-18118/com.androidbook.fragments.dialogs V/FragmentManager﹕ movefrom STARTED: DialogFragment{41cc3a60 #0 Tag1}
08-01 21:40:19.121 18118-18118/com.androidbook.fragments.dialogs V/FragmentManager﹕ movefrom ACTIVITY_CREATED: DialogFragment{41cc3a60 #0 Tag1}
08-01 21:40:19.121 18118-18118/com.androidbook.fragments.dialogs V/FragmentManager﹕ movefrom CREATED: DialogFragment{41cc3a60 #0 Tag1}
08-01 21:40:19.121 18118-18118/com.androidbook.fragments.dialogs V/FragmentManager﹕ Freeing fragment index DialogFragment{41cc3a60 #0 Tag1}

先是提交两条 BSR，可以看到不是提交后就立即执行的，而是处理 Message 队列那样。

之后的过程和前面是一样的，也许根本就没节约多少开销。

    @Override    public void onClick(View view) {        dialogFragment.show(getFragmentManager(), "Tag1");        dialogFragment.show(getFragmentManager(), "Tag1");    }

08-01 21:44:08.336 18611-18611/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Commit: android.app.BackStackRecord@41ce94e8
08-01 21:44:08.336 18611-18611/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Commit: android.app.BackStackRecord@41ce97c0
08-01 21:44:08.341 18611-18611/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Run: android.app.BackStackRecord@41ce94e8
08-01 21:44:08.341 18611-18611/com.androidbook.fragments.dialogs V/FragmentManager﹕ add: DialogFragment{41cbdf88 Tag1}
08-01 21:44:08.341 18611-18611/com.androidbook.fragments.dialogs V/FragmentManager﹕ Allocated fragment index DialogFragment{41cbdf88 #0 Tag1}
08-01 21:44:08.346 18611-18611/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto CREATED: DialogFragment{41cbdf88 #0 Tag1}
08-01 21:44:08.346 18611-18611/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto ACTIVITY_CREATED: DialogFragment{41cbdf88 #0 Tag1}
08-01 21:44:08.346 18611-18611/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto STARTED: DialogFragment{41cbdf88 #0 Tag1}
08-01 21:44:08.376 18611-18611/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto RESUMED: DialogFragment{41cbdf88 #0 Tag1}
08-01 21:44:08.381 18611-18611/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Run: android.app.BackStackRecord@41ce97c0
08-01 21:44:08.381 18611-18611/com.androidbook.fragments.dialogs V/FragmentManager﹕ add: DialogFragment{41cbdf88 #0 Tag1}

提交两条 BSR， FM add DF 41cbdf88 Tag1 ----- add DF 41cbdf88 #0 Tag1

显示效果方面已经崩了，可以发现 41dbdf88 是一样的，也许就是地址或地址的映射。

这告诉我们，不要 add 已经 add 过的 DF。

@Override    public void onClick(View view) {        dialogFragment.show(getFragmentManager(), "Tag1");        dialogFragment.show(getFragmentManager(), "Tag2");    }

java.lang.IllegalStateException: Can't change tag of fragment DialogFragment{41cba5d8 Tag1}: was Tag1 now Tag2

这下抛异常了，这是我唯一见过会抛异常的可能。

就是说地址和 Tag 是唯一绑定的。

    @Override    public void onClick(View view) {        new DialogFragment().show(getFragmentManager(),"Tag1");        new DialogFragment().show(getFragmentManager(),"Tag1");    }

没有任何问题，说明 Tag 并不需要唯一，而是对于同一个 Fragment 需要用唯一的 Tag 来绑定。

08-01 21:52:50.556 20073-20073/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Commit: android.app.BackStackRecord@41cdb2c0
08-01 21:52:50.556 20073-20073/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Commit: android.app.BackStackRecord@41cdb778
08-01 21:52:50.556 20073-20073/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Run: android.app.BackStackRecord@41cdb2c0
08-01 21:52:50.561 20073-20073/com.androidbook.fragments.dialogs V/FragmentManager﹕ add: DialogFragment{41cdb1b8 Tag1}
08-01 21:52:50.561 20073-20073/com.androidbook.fragments.dialogs V/FragmentManager﹕ Allocated fragment index DialogFragment{41cdb1b8 #0 Tag1}
08-01 21:52:50.561 20073-20073/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto CREATED: DialogFragment{41cdb1b8 #0 Tag1}
08-01 21:52:50.561 20073-20073/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto ACTIVITY_CREATED: DialogFragment{41cdb1b8 #0 Tag1}
08-01 21:52:50.561 20073-20073/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto STARTED: DialogFragment{41cdb1b8 #0 Tag1}
08-01 21:52:50.571 20073-20073/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto RESUMED: DialogFragment{41cdb1b8 #0 Tag1}
08-01 21:52:50.571 20073-20073/com.androidbook.fragments.dialogs V/BackStackEntry﹕ Run: android.app.BackStackRecord@41cdb778
08-01 21:52:50.571 20073-20073/com.androidbook.fragments.dialogs V/FragmentManager﹕ add: DialogFragment{41cdb6b0 Tag1}
08-01 21:52:50.571 20073-20073/com.androidbook.fragments.dialogs V/FragmentManager﹕ Allocated fragment index DialogFragment{41cdb6b0 #1 Tag1}
08-01 21:52:50.571 20073-20073/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto CREATED: DialogFragment{41cdb6b0 #1 Tag1}
08-01 21:52:50.571 20073-20073/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto ACTIVITY_CREATED: DialogFragment{41cdb6b0 #1 Tag1}
08-01 21:52:50.571 20073-20073/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto STARTED: DialogFragment{41cdb6b0 #1 Tag1}
08-01 21:52:50.581 20073-20073/com.androidbook.fragments.dialogs V/FragmentManager﹕ moveto RESUMED: DialogFragment{41cdb6b0 #1 Tag1}

他们的 Tag 是一样的，但地址不同。

那么如果调用 findFragmentByTag 会取到哪个呢？

事实上会拿到后添加的那个，并不会抛出异常。

所以，要注意的就是不要改变的 DF 的 Tag。

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