Question

[编辑]当我尝试在Intent构造函数中使用“this”切换出“v.getContext（）”时，Eclipse说它无法构建应用程序。调用onClick（）方法时当前的View是否传递给它？

[编辑2]我可能已经找到了问题所在。可能是因为我在使用Android 2.3.3模拟器时使用的是适用于Android 3.0的布局。就是那个，或者我只使用字符串数组而不是整数数组。

在我的Android应用中，当用户点击按钮将其带到选项卡式活动时，我正在运行的模拟器（使用Android 2.3.3）强制关闭我的应用。这是最初的活动。

DungeonsDragonsAppActivity.java文件

package com.androidGuy.DnDApp;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import android.util.Log;

public class DungeonsDragonsAppActivity extends Activity {

    /* Use this for debugging. */
    private static final String DEBUG_TAG = "DnDAppDebugLogging";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

    /* The main buttons... Yeah. */
        final Button create_character_button = (Button) findViewById(R.id.createCharacterButton);
            final Button open_character_button = (Button) findViewById(R.id.openCharacterButton);
        final Button retrieve_character_button = (Button) findViewById(R.id.RetrieveCharacterButton);

        /* The button for actually creating the character.. */
        create_character_button.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                try {
                    Intent intent = new Intent(v.getContext(),
                            CreateCharacterTabsActivity.class);
                    startActivityForResult(intent, 0);
                } catch (Exception e) {
                    Log.e(DEBUG_TAG, "Click failed", e);
                }
            }
        });

        /* The button for opening a pre-existing character. */
        open_character_button.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Toast.makeText(DungeonsDragonsAppActivity.this,
                        "You will be able to open a character... Eventually.",
                        Toast.LENGTH_SHORT).show();
            }
        });

        /* The button for importing from D & D insider. */
        retrieve_character_button
                .setOnClickListener(new View.OnClickListener() {
                    public void onClick(View v) {
                        Toast.makeText(
                                DungeonsDragonsAppActivity.this,
                                "You will be able to import characters... Hopefully.",
                                Toast.LENGTH_SHORT).show();
                    }
                }

                );
    }
}

当用户点击按钮创建新角色时，它应该加载此活动：

CreateCharacterTabsActivity.java

package com.androidGuy.DnDApp;

import android.app.TabActivity;
import android.os.Bundle;
import android.widget.TabHost;
import android.content.Intent;

public class CreateCharacterTabsActivity extends TabActivity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        TabHost tabHost = getTabHost();
        TabHost.TabSpec spec;
        Intent intent;

        // Initialize a TabSpec for each tab and add it to the TabHost.
        spec = tabHost.newTabSpec("scores");
        spec.setContent(new Intent().setClass(this,
                CharacterAbilityScoresActivity.class));
        spec.setIndicator("Scores");
        tabHost.addTab(spec);

        intent = new Intent().setClass(this, CharacterClassActivity.class);
        spec = tabHost.newTabSpec("classes");
        spec.setContent(intent);
        spec.setIndicator("Classes");
        tabHost.addTab(spec);

        tabHost.setCurrentTab(0);
    }

}

它使用此XML文件来呈现选项卡（我从Android开发教程之一中获取了它）。

tabs.xml

<?xml version="1.0" encoding="utf-8"?>
<TabHost xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@android:id/tabhost"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <LinearLayout
        android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:padding="5dp">

        <FrameLayout
            android:id="@android:id/tabcontent"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:padding="5dp"
            android:layout_weight="1">

        </FrameLayout>

        <TabWidget
            android:id="@android:id/tabs"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_weight="0">
        </TabWidget>

    </LinearLayout>

</TabHost>

加载该活动后，还应将这些活动加载到选项卡中。

CharacterAbilityScoresActivity.java

package com.androidGuy.DnDApp;

import android.app.Activity;
import android.os.Bundle;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.Toast;
import android.view.View;

public class CharacterAbilityScoresActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.ability_score_spinners); // Set the scene.

        ArrayAdapter adapter = ArrayAdapter.createFromResource(this, R.array.ability_scores, android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        /* The ability score spinners */
        Spinner strengthSpinner = (Spinner) findViewById(R.id.StrengthSpinner);
        strengthSpinner.setAdapter(adapter);
        strengthSpinner
                .setOnItemSelectedListener(new abilityScoreListSelectedListener());

        Spinner constitutionSpinner = (Spinner) findViewById(R.id.ConstitutionSpinner);
        constitutionSpinner.setAdapter(adapter);
        constitutionSpinner
                .setOnItemSelectedListener(new abilityScoreListSelectedListener());
    }

    /* Now let's see what the user selects. */
    class abilityScoreListSelectedListener implements OnItemSelectedListener {
        public void onItemSelected(AdapterView<?> parent, View view, int pos,
                long id) {
            Toast.makeText(parent.getContext(),
                    "You selected an ability score.  Way to go.",
                    Toast.LENGTH_LONG).show();
        }

        public void onNothingSelected(AdapterView parent) {
            // Do nothing... For now.
        }
    }
}

ability_score_spinners.xml

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout android:id="@+id/linearLayout1" android:layout_width="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android" android:layout_height="match_parent">
        <TableLayout android:layout_height="match_parent" android:id="@+id/tableLayout1" android:layout_width="wrap_content">
            <TableRow android:id="@+id/tableRow1" android:layout_width="wrap_content" android:layout_height="match_parent">
                <Spinner android:layout_height="wrap_content" android:minWidth="10dip" android:layout_width="wrap_content" android:layout_gravity="left" android:layout_weight="1" android:id="@+id/StrengthSpinner" android:entries="@array/ability_scores" android:prompt="@string/ability_score_prompt"></Spinner>
            </TableRow>
            <TableRow android:id="@+id/tableRow2" android:layout_width="wrap_content" android:layout_height="wrap_content">
                <Spinner android:layout_height="wrap_content" android:layout_weight="1" android:layout_width="wrap_content" android:id="@+id/ConstitutionSpinner" android:entries="@array/ability_scores" android:prompt="@string/ability_score_prompt"></Spinner>
            </TableRow>
            <TableRow android:id="@+id/tableRow4" android:layout_width="wrap_content" android:layout_height="wrap_content"></TableRow>
            <TableRow android:layout_height="wrap_content" android:id="@+id/tableRow3" android:layout_width="wrap_content">
            </TableRow>
        </TableLayout>
        <TableLayout android:layout_height="match_parent" android:id="@+id/tableLayout2" android:layout_width="match_parent">
            <TableRow android:id="@+id/tableRow5" android:layout_width="wrap_content" android:layout_height="wrap_content">
                <TextView android:text="@string/strengthText" android:layout_height="wrap_content" android:textAppearance="?android:attr/textAppearanceLarge" android:id="@+id/StrengthText"></TextView>
            </TableRow>
            <TableRow android:id="@+id/tableRow6" android:layout_width="wrap_content" android:layout_height="wrap_content">
                <TextView android:layout_height="wrap_content" android:layout_width="wrap_content" android:textAppearance="?android:attr/textAppearanceLarge" android:id="@+id/textView1" android:text="@string/constitionText"></TextView>
            </TableRow>
            <TableRow android:id="@+id/tableRow7" android:layout_width="wrap_content" android:layout_height="wrap_content"></TableRow>
            <TableRow android:id="@+id/tableRow8" android:layout_width="wrap_content" android:layout_height="wrap_content">
            </TableRow>
        </TableLayout>
    </LinearLayout>

CharacterClassesActivity.java

package com.androidGuy.DnDApp;

import android.app.Activity;
import android.os.Bundle;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;

public class CharacterClassActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.cha_classes);

        final RadioGroup classesButtons = (RadioGroup) findViewById(R.id.radioGroup1);
        classesButtons
                .setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
                    public void onCheckedChanged(RadioGroup group, int checkedId) {
                        TextView leTextView = (TextView) findViewById(R.id.chooseClassTextView);
                        if (checkedId != -1) {
                            RadioButton rb = (RadioButton) findViewById(checkedId);

                            if (rb != null) {
                                leTextView.setText("You chose: " + rb.getText());
                            }
                        } else {
                            leTextView.setText("Choose your class");
                        }
                    }
                });
    }
}

cha_classes.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:id="@+id/linearLayout1" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" xmlns:android="http://schemas.android.com/apk/res/android">
   <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:textAppearance="?android:attr/textAppearanceLarge" android:text="Choose your class" android:id="@+id/chooseClassTextView"></TextView>

    <RadioGroup android:id="@+id/radioGroup1" android:layout_width="wrap_content" android:layout_height="wrap_content">
        <RadioButton android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/ClericClassButton" android:text="Cleric"></RadioButton>
        <RadioButton android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/FighterClassButton" android:text="Fighter"></RadioButton>
        <RadioButton android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/PaladinClassButton" android:text="Paladin"></RadioButton>
        <RadioButton android:layout_width="wrap_content" android:text="Ranger" android:layout_height="wrap_content" android:id="@+id/RangerClassButton"></RadioButton>
        <RadioButton android:layout_width="wrap_content" android:text="Rogue" android:layout_height="wrap_content" android:id="@+id/RogueClassButton"></RadioButton>
        <RadioButton android:layout_width="wrap_content" android:text="Warlock" android:layout_height="wrap_content" android:id="@+id/WarlockClassButton"></RadioButton>
        <RadioButton android:layout_width="wrap_content" android:text="Warlord" android:layout_height="wrap_content" android:id="@+id/WarlordClassButton"></RadioButton>
        <RadioButton android:layout_width="wrap_content" android:text="Wizard" android:layout_height="wrap_content" android:id="@+id/WizardClassButton"></RadioButton>
    </RadioGroup>
</LinearLayout>

能力分数应位于第一个选项卡中，而字符类应位于第二个选项卡中。我在res / values /目录中编写了一个整数数组，并尝试在与能力分数一起使用的微调器中使用它。

起初我认为这是标签布局及其处理方式。它应该做的就是设置选项卡并用适当的活动填充它。我还以为我在CreateCharacterTabsActivity中缺少一个setContentView（）方法。但事实并非如此。我还认为这是由于我的清单缺少一些活动条目，但这也是不正确的。

的AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      android:versionCode="1"
      android:versionName="1.0" package="com.androidGuy.DnDApp">
    <uses-sdk android:minSdkVersion="10" />

    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".DungeonsDragonsAppActivity"
                  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=".CreateCharacterTabsActivity" android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <action android:name="android.intent.category.LAUNCHER"></action>
            </intent-filter>
        </activity>
        <activity android:name=".CharacterAbilityScoresActivity"></activity>
        <activity android:name=".CharacterClassActivity"></activity>

    </application>
</manifest>

然后，似乎错误可能与我如何处理微调器的整数数据有关。我创建了一个ArrayAdapter来接受整数数据，并在微调器中设置数据。不过，当我运行模拟器时，它仍然会崩溃。

这是崩溃时的LogCat堆栈跟踪。

ERROR/AndroidRuntime(363): FATAL EXCEPTION: main
ERROR/AndroidRuntime(363): java.lang.NullPointerException
ERROR/AndroidRuntime(363):     at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:355)
ERROR/AndroidRuntime(363):     at android.widget.ArrayAdapter.getView(ArrayAdapter.java:323)
ERROR/AndroidRuntime(363):     at android.widget.AbsSpinner.onMeasure(AbsSpinner.java:192)
ERROR/AndroidRuntime(363):     at android.view.View.measure(View.java:8313)
ERROR/AndroidRuntime(363):     at android.widget.TableRow.getColumnsWidths(TableRow.java:308)
ERROR/AndroidRuntime(363):     at android.widget.TableLayout.findLargestCells(TableLayout.java:500)
ERROR/AndroidRuntime(363):     at android.widget.TableLayout.measureVertical(TableLayout.java:465)
ERROR/AndroidRuntime(363):     at android.widget.TableLayout.onMeasure(TableLayout.java:431)
ERROR/AndroidRuntime(363):     at android.view.View.measure(View.java:8313)
ERROR/AndroidRuntime(363):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
ERROR/AndroidRuntime(363):     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1017)
ERROR/AndroidRuntime(363):     at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:701)
ERROR/AndroidRuntime(363):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:311)
ERROR/AndroidRuntime(363):     at android.view.View.measure(View.java:8313)
ERROR/AndroidRuntime(363):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
ERROR/AndroidRuntime(363):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
ERROR/AndroidRuntime(363):     at android.view.View.measure(View.java:8313)
ERROR/AndroidRuntime(363):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
ERROR/AndroidRuntime(363):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
ERROR/AndroidRuntime(363):     at android.view.View.measure(View.java:8313)
ERROR/AndroidRuntime(363):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
ERROR/AndroidRuntime(363):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
ERROR/AndroidRuntime(363):     at android.view.View.measure(View.java:8313)
ERROR/AndroidRuntime(363):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:531)
ERROR/AndroidRuntime(363):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
ERROR/AndroidRuntime(363):     at android.view.View.measure(View.java:8313)
ERROR/AndroidRuntime(363):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
ERROR/AndroidRuntime(363):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
ERROR/AndroidRuntime(363):     at android.view.View.measure(View.java:8313)
ERROR/AndroidRuntime(363):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
ERROR/AndroidRuntime(363):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
ERROR/AndroidRuntime(363):     at android.view.View.measure(View.java:8313)
ERROR/AndroidRuntime(363):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:531)
ERROR/AndroidRuntime(363):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
ERROR/AndroidRuntime(363):     at android.view.View.measure(View.java:8313)
ERROR/AndroidRuntime(363):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
ERROR/AndroidRuntime(363):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
ERROR/AndroidRuntime(363):     at android.view.View.measure(View.java:8313)
ERROR/AndroidRuntime(363):     at android.view.ViewRoot.performTraversals(ViewRoot.java:839)
ERROR/AndroidRuntime(363):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
ERROR/AndroidRuntime(363):     at android.os.Handler.dispatchMessage(Handler.java:99)
ERROR/AndroidRuntime(363):     at android.os.Looper.loop(Looper.java:123)
ERROR/AndroidRuntime(363):     at android.app.ActivityThread.main(ActivityThread.java:3683)
ERROR/AndroidRuntime(363):     at java.lang.reflect.Method.invokeNative(Native Method)
ERROR/AndroidRuntime(363):     at java.lang.reflect.Method.invoke(Method.java:507)
ERROR/AndroidRuntime(363):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
ERROR/AndroidRuntime(363):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
ERROR/AndroidRuntime(363):     at dalvik.system.NativeStart.main(Native Method)

感谢您提供的任何见解。

Answer 1

您似乎在清单中定义了两个启动器活动：

...
<activity android:name=".DungeonsDragonsAppActivity"
          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=".CreateCharacterTabsActivity" android:label="@string/app_name">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <action android:name="android.intent.category.LAUNCHER"></action>
    </intent-filter>
</activity>
...

这可能会导致TabManager崩溃。

Answer 2

小心使用内部类中的this！我经常犯这个错误，通常与传递Context有关！请务必使用正确的语法转到“外部”this，例如MyOuterClass.this。

单击按钮以加载Tab布局后应用程序崩溃

2 个答案: