如何在Java创建的布局中创建地图片段（GoogleMap）？

Question

我试图在Java创建的布局中创建一个地图（GoogleMap）。我不明白为什么在尝试从LinearLayout获取ID时会出现与imageView相关的错误。

这是我的代码：

        LinearLayout mapLayout = new LinearLayout(customToursActivity);
        mapLayout.setId(rootView.generateViewId());
        mapLayout.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, 0, 0.5f));
        layout.addView(mapLayout);

        FragmentManager fm = getChildFragmentManager();
        SupportMapFragment supportMapFragment =  SupportMapFragment.newInstance();
        fm.beginTransaction().replace(mapLayout.getId(), supportMapFragment).commit();

这是我得到的日志：

01-22 15:04:28.034  19341-19341/abff.googlemapsappteste E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: abff.googlemapsappteste, PID: 19341
    java.lang.ClassCastException: android.widget.ImageView cannot be cast to android.view.ViewGroup
            at android.support.v4.app.BackStackRecord.configureTransitions(BackStackRecord.java:1134)
            at android.support.v4.app.BackStackRecord.beginTransition(BackStackRecord.java:1041)
            at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:661)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1501)
            at android.support.v4.app.Fragment.performStart(Fragment.java:1810)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:989)
            at android.support.v4.app.FragmentManagerImpl.performPendingDeferredStart(FragmentManager.java:846)
            at android.support.v4.app.FragmentManagerImpl.startPendingDeferredFragments(FragmentManager.java:1162)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1518)
            at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:490)
            at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
            at android.support.v4.view.ViewPager.populate(ViewPager.java:1105)
            at android.support.v4.view.ViewPager.populate(ViewPager.java:951)
            at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1473)
            at android.view.View.measure(View.java:17637)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
            at android.support.v7.internal.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:124)
            at android.view.View.measure(View.java:17637)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
            at android.support.v7.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:444)
            at android.view.View.measure(View.java:17637)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
            at android.view.View.measure(View.java:17637)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
            at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
            at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
            at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
            at android.view.View.measure(View.java:17637)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
            at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2618)
            at android.view.View.measure(View.java:17637)
            at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2019)
            at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1177)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1383)
            at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1065)
            at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5901)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
            at android.view.Choreographer.doCallbacks(Choreographer.java:580)
            at android.view.Choreographer.doFrame(Choreographer.java:550)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:211)
            at android.app.ActivityThread.main(ActivityThread.java:5389)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1020)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:815)

Answer 1

我也遇到了同样的问题，但需要一个不同的解决方法。和您一样，我有一个定制视图，它正在以编程方式创建一个SupportMapFragment。但是在我的例子中，这个视图可能在一个RecyclerView项中，因此使用链接到的方法生成一个新的Id（它在while循环中使用findViewById查找下一个可用Id）将无法工作，因为视图每次都获得相同的Id，因为它在自己的子视图层次结构中调用findViewById。相同的Id是不好的，因为当我在自定义视图中使用片段管理器进行替换时，它每次只替换第一个出现的，即第一个RecyclerView项。

我在Google maps lib中发现了一个bug，它似乎在内部使用了一些生成的ID，这与View.generateViewId（）中生成的第一个可用ID冲突，这导致我尝试了这个方法，从而解决了这个问题：

int newViewId = -1;
int loopCount = 0;

// I tried starting at 70, actual number used internally in Google maps may be lower
while (loopCount < 70) {
    loopCount++;
    if (ApiLevelHelper.SameOrNewer(17)) {
        // using https://gist.github.com/omegasoft7/fdf7225a5b2955a1aba8
        newViewId = ViewHelper.generateViewId();
    } else {
        newViewId = View.generateViewId();
    }
}

FrameLayout mapFrameLayout = new FrameLayout(getContext());
mapFrameLayout.setLayoutParams(new FrameLayout.LayoutParams(FrameLayout.LayoutParams.MATCH_PARENT, FrameLayout.LayoutParams.MATCH_PARENT));
mapFrameLayout.setId(newViewId);

FrameLayout pnlMapFragment = (FrameLayout)findViewById(R.id.pnlMapFragment);
pnlMapFragment.addView(mapFrameLayout);

((AppCompatActivity) getContext()).getSupportFragmentManager().beginTransaction()
                    .replace(mapFrameLayout.getId(), this.mapFragment)
                    .commit();

this.mapFragment.getMapAsync(this);