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)
最佳答案
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");
}
}
关于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，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/32687470/