android - 使用 Material Design 当程序从启动器 Activity 转到另一个时应用程序崩溃

Question

我正在尝试在我现有的一个项目上实现 Material Design，主题在启动器 Activity 上运行良好，但当我导航到另一个 Activity 时，应用程序崩溃了。

list 文件

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.mycompany.hsclock" >

    <uses-feature android:name="android.hardware.camera" />

    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.CAMERA" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:largeHeap="true"
        android:theme="@style/MyMaterialTheme" >
        <activity
            android:name=".MainActivity"
            android:configChanges="keyboardHidden|orientation|screenSize"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>

        </activity>
        <activity
            android:name=".CategoryActivity"
            android:label="@string/title_activity_category"
            android:parentActivityName=".MainActivity" >
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.mycompany.hsclock.MainActivity" />
        </activity>
        <activity
            android:name=".SwipeViews.SwipeView"
            android:label="@string/title_activity_swipe_view" >
        </activity>
        <activity
            android:name=".SaveOnShare.SaveShare"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.SEND" />

                <category android:name="android.intent.category.DEFAULT" />

                <data android:mimeType="image/*" />
            </intent-filter>
            <intent-filter>
                <action android:name="android.intent.action.SEND_MULTIPLE" />

                <category android:name="android.intent.category.DEFAULT" />

                <data android:mimeType="image/*" />
            </intent-filter>
        </activity>
    </application>

</manifest>

样式.xml

<style name="MyMaterialTheme" parent="MyMaterialTheme.Base" >
        <item name = "android:icon">@drawable/ic_launcher</item></style>

<style name="MyMaterialTheme.Base" parent="Theme.AppCompat.Light.NoActionBar">

        <item name="android:windowNoTitle">true</item>
        <item name="android:windowActionBar">false</item>
        <item name="android:colorPrimary">@color/primary</item>
        <item name="android:colorPrimaryDark">@color/primary_dark</item>
        <item name="android:colorAccent">@color/accent</item>

    </style>

values-v21, styles.xml

<resources>

    <style name="MyMaterialTheme" parent="MyMaterialTheme.Base">
        <item name="android:windowContentTransitions">true</item>
        <item name="android:windowAllowEnterTransitionOverlap">true</item>
        <item name="android:windowAllowReturnTransitionOverlap">true</item>
        <item name="android:windowSharedElementEnterTransition">@android:transition/move</item>
        <item name="android:windowSharedElementExitTransition">@android:transition/move</item>
    </style>

</resources>

主要 Activity

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        Toolbar mtoolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(mtoolbar);

        initCategoryList();
        createCategoryPopup();
        populateCategoryList();
    }

调用第二个 Activity 的方法

private void initCategoryList()
    {

        listView = (ListView) findViewById(R.id.list);
        mCategoryAdapter=new CategoryAdapter(this,mCategoryItems);

        // Assign adapter to ListView
        listView.setAdapter(mCategoryAdapter);

        listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {

            public boolean onItemLongClick(AdapterView<?> parent,
                                           View view, int position, long id) {
                onListItemSelect(position);
                return true;
            }
        });

        // ListView Item Click Listener
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                                    int position, long id) {

                if (mActionMode == null) {
                    // ListView Clicked item index
                    int itemPosition = position;

                    // ListView Clicked item value
                    CategoryItem itemValue = (CategoryItem) parent.getItemAtPosition(position);

                    // Show Alert
                    Toast.makeText(getApplicationContext(),
                            "Position :" + itemPosition + "  ListItem : " + itemValue.name, Toast.LENGTH_LONG)
                            .show();


                    Intent categoryintent = new Intent(getBaseContext(), CategoryActivity.class);

                    if (itemValue != null) {
                        categoryintent.putExtra("cat_id", itemValue.id);
                        categoryintent.putExtra("cat_name", itemValue.name);
                    }
                    startActivity(categoryintent);
                } else
                    // add or remove selection for current list item
                    onListItemSelect(position);

            }

        });


    }

第二个 Activity

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Toolbar mtoolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(mtoolbar);

        // Catching intent of the selected category
        Intent data = getIntent();
        if(data !=  null){
            catId = data.getIntExtra("cat_id", -1);
            catName = data.getStringExtra("cat_name");

        }

第二个 Activity xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"
    android:layout_height="match_parent"

    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"

    android:orientation="vertical"
    tools:context=".MainActivity">


    <include
        android:id="@+id/toolbar"
        layout="@layout/toolbar"/>

    <ListView
        android:id="@+id/list"
        android:layout_weight="10"
        android:layout_height="100dp"
        android:layout_width="match_parent">
    </ListView>

</LinearLayout>

错误日志

Caused by: java.lang.NullPointerException
            at android.support.v7.internal.widget.ToolbarWidgetWrapper.<init>(ToolbarWidgetWrapper.java:94)
            at android.support.v7.internal.widget.ToolbarWidgetWrapper.<init>(ToolbarWidgetWrapper.java:87)
            at android.support.v7.internal.app.ToolbarActionBar.<init>(ToolbarActionBar.java:79)
            at android.support.v7.app.AppCompatDelegateImplV7.setSupportActionBar(AppCompatDelegateImplV7.java:198)
            at android.support.v7.app.AppCompatActivity.setSupportActionBar(AppCompatActivity.java:96)
            at com.mycompany.hsclock.CategoryActivity.onCreate(CategoryActivity.java:71)
            at android.app.Activity.performCreate(Activity.java:5372)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2257)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349)
            at android.app.ActivityThread.access$700(ActivityThread.java:159)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:176)
            at android.app.ActivityThread.main(ActivityThread.java:5419)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

试试这个 -

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_category);

    View myView = findViewById(R.id.toolbar);
    Toolbar mtoolbar = (Toolbar) myView.findViewById(R.id.toolbar);
    setSupportActionBar(mtoolbar);

    // Catching intent of the selected category
    Intent data = getIntent();
    if(data !=  null){
        catId = data.getIntExtra("cat_id", -1);
        catName = data.getStringExtra("cat_name");

    }
}