Question

你好，我刚刚开始编写代码，我构建了一个计数器应用程序，但是它既不在我的模拟器上也不在我的Android手机上运行。任何帮助请

这是xml代码（activity_main.xml）

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="vertical">

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:padding="16dp"
                android:text="@string/team_a"
                android:textColor="@color/colorAccent"
                android:textSize="14sp"
                app:fontFamily="cursive" />

            <TextView
                android:id="@+id/team_a_score"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:paddingBottom="24dp"
                android:text="@string/_0"
                android:textColor="@color/colorAccent"
                android:textSize="56sp"
                app:fontFamily="cursive" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginLeft="24dp"
                android:layout_marginRight="24dp"
                android:layout_marginBottom="8dp"
                android:onClick="addThreeForTeamA"
                android:text="@string/_3_points" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginLeft="24dp"
                android:layout_marginRight="24dp"
                android:layout_marginBottom="8dp"
                android:onClick="addTwoForTeamA"
                android:text="@string/_2_points" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginLeft="24dp"
                android:layout_marginRight="24dp"
                android:layout_marginBottom="8dp"
                android:onClick="addOneForTeamA"
                android:text="@string/free_throw" />
        </LinearLayout>
        <view
            android:layout_width="1dp"
            android:layout_height="match_parent"
            android:layout_marginTop="16dp"
            android:background="@android:color/holo_blue_bright" />

        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="vertical">

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:fontFamily="cursive"
                android:gravity="center"
                android:padding="16dp"
                android:text="@string/team_b"
                android:textColor="#FF1C25C8"
                android:textSize="14sp" />

            <TextView
                android:id="@+id/team_b_score"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:fontFamily="cursive"
                android:gravity="center"
                android:paddingBottom="24dp"
                android:text="@string/_0"
                android:textColor="#FF1C25C8"
                android:textSize="56sp" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginLeft="24dp"
                android:layout_marginRight="24dp"
                android:layout_marginBottom="8dp"
                android:onClick="addThreeForTeamB"
                android:text="@string/_3_points" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginLeft="24dp"
                android:layout_marginRight="24dp"
                android:layout_marginBottom="8dp"
                android:onClick="addTwoForTeamB"
                android:text="@string/_2_points" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginLeft="24dp"
                android:layout_marginRight="24dp"
                android:layout_marginBottom="8dp"
                android:onClick="addOneForTeamB"
                android:text="@string/free_throw" />
        </LinearLayout>
    </LinearLayout>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginLeft="24dp"
        android:layout_marginRight="24dp"
        android:layout_marginBottom="8dp"
        android:onClick="resetScore"
        android:text="@string/reset" />
</RelativeLayout>

Java代码如下（MainActivity.java）

package com.example.monsurah.counter;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
int scoreTeamA = 0;
int scoreTeamB = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(com.example.monsurah.counter.R.layout.activity_main);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
    /**
     *Adds one for Team A
     */
    public void addOneForTeamA (View v) {
        scoreTeamA = scoreTeamA + 1;
        displayForTeamA(scoreTeamA);
    }
    /**
     *Adds two for Team A
     */
    public void addTwoForTeamA (View v) {
        scoreTeamA = scoreTeamA + 2;
        displayForTeamA(scoreTeamA);
    } /**
     *Adds three for Team A
     */
    public void addThreeForTeamA (View v) {
        scoreTeamA = scoreTeamA + 3;
        displayForTeamA(scoreTeamA);
    } /**
     *Adds one for Team B
     */
    public void addOneForTeamB (View v) {
        scoreTeamB = scoreTeamB + 1;
        displayForTeamB(scoreTeamB);
    } /**
     *Adds two for Team B
     */
    public void addTwoForTeamB (View v) {
        scoreTeamB = scoreTeamB + 2;
        displayForTeamB(scoreTeamB);
    } /**
     *Adds three for Team B
     */
    public void addThreeForTeamB (View v) {
        scoreTeamB = scoreTeamB + 3;
        displayForTeamB(scoreTeamB);
    }
    /**
     *Reset Scores
     */
    public void resetScore (View v) {
        scoreTeamA = 0;
        scoreTeamB = 0;
        displayForTeamB(scoreTeamB);
        displayForTeamB(scoreTeamB);
    }
    /**
     * Displays the given score for Team A.
     */
    public void displayForTeamA(int score) {
        TextView scoreView = (TextView) findViewById(R.id.team_a_score);
        scoreView.setText(String.valueOf(score));
    }
    /**
     * Displays the given score for Team B.
     */
    public void displayForTeamB(int score) {
        TextView scoreView = (TextView) findViewById(R.id.team_b_score);
        scoreView.setText(String.valueOf(score));
    }
}

我收到的错误消息是

原因：android.view.InflateException：二进制XML文件第68行：尝试调用虚拟方法'boolean 空对象引用上的java.lang.String.equals（java.lang.Object）' 引起原因：java.lang.NullPointerException：尝试在其上调用虚拟方法'boolean java.lang.String.equals（java.lang.Object）' 空对象引用在android.view.LayoutInflater.createViewFromTag（LayoutInflater.java:768）在android.view.LayoutInflater.createViewFromTag（LayoutInflater.java:734）在android.view.LayoutInflater.rInflate（LayoutInflater.java:865）在android.view.LayoutInflater.rInflateChildren（LayoutInflater.java:828）在android.view.LayoutInflater.rInflate（LayoutInflater.java:873）在android.view.LayoutInflater.rInflateChildren（LayoutInflater.java:828）在android.view.LayoutInflater.inflate（LayoutInflater.java:525）在android.view.LayoutInflater.inflate（LayoutInflater.java:427）在android.view.LayoutInflater.inflate（LayoutInflater.java:378）在android.support.v7.app.AppCompatDelegateImplV9.setContentView（AppCompatDelegateImplV9.java:287）在android.support.v7.app.AppCompatActivity.setContentView（AppCompatActivity.java:139）在com.example.monsurah.counter.MainActivity.onCreate（MainActivity.java:16）在android.app.Activity.performCreate（Activity.java:6942）在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1126）在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2910）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:3018）在android.app.ActivityThread.-wrap14（ActivityThread.java）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1653）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:154）在android.app.ActivityThread.main（ActivityThread.java:6724）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:1520）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:1410）

Answer 1

在布局中将view更改为View。

    <view
        android:layout_width="1dp"
        ... />

到

    <View
        android:layout_width="1dp"
        ... />

建议：有关一线解决方案，请参见@ myanswer。

我的应用程序未在手机或仿真器上运行

1 个答案: