我有一个包含Texts的数据库。我的活动在顶部有一个TextView（这应该始终保持完整），而在下面我有一个RelativeLayout，它将是我的容器。在我的代码中，只要活动（我将动态插入视图）启动，我就创建一个LinearLayoutCompact对象并设置一些属性。然后我将光标处理到表数据，我为每个数据库元素创建一个TextView，并将其添加到LinearLayoutCompat对象。最后，我尝试将此对象添加到应用程序崩溃的RelativeLayout容器中。我正在使用LayoutInflater并将RelativeLayout容器视为ViewGroup（我在做了一些研究后发现了这种方式）。但是，如果我只是在LinearLayoutCompat对象上使用setContentView它工作正常，但也替换了我想要出现的TextView。以下是我认为必要的文件：
veg_option.xml （我的活动布局）
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView <!-- The one I want intact throughout -->
android:id="@+id/narrowText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Let's narrow down now !"
android:textSize="20sp"
android:textColor="@color/wineBrown"
android:gravity="center"
android:padding="10dp"
android:layout_marginTop="30dp"
android:elevation="4dp"/>
<RelativeLayout <!-- Trying to use this as container -->
android:id="@+id/dataCont"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center">
</RelativeLayout>
</LinearLayout>
VegOptions.java （应该发生所有行动的活动）
package com.techpappy.whattoeat;
/**
* Created by Mehul on 31-05-2017.
*/
import android.content.Context;
import android.database.Cursor;
import android.graphics.Color;
import android.graphics.Typeface;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutCompat;
import android.support.v7.widget.AppCompatTextView;
import android.util.TypedValue;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.os.Bundle;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
import org.w3c.dom.Text;
import java.util.ArrayList;
public class VegOptions extends AppCompatActivity{
protected DBSource vegDBSource;
private Cursor cursor;
protected ArrayList<String> mTypes;
LayoutInflater li = (LayoutInflater)getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View v = li.inflate(R.layout.veg_option, null);
ViewGroup dataConPt = (ViewGroup) findViewById(R.id.dataCont);
@Override
public void onCreate(Bundle bundle) {
super.onCreate(bundle);
setContentView(R.layout.veg_option);
vegDBSource = new DBSource(VegOptions.this);
disp();
}
private void disp()
{
vegDBSource.open();
cursor = vegDBSource.getInfo();
LinearLayoutCompat linearLayoutCompat = defaultPage(cursor);
//setContentView(linearLayoutCompat); Works fine but replaces all
dataConPt.addView(linearLayoutCompat);
}
//Here my LinearLayoutCompat object is prepared and returned
public LinearLayoutCompat defaultPage(Cursor mCursor) {
LinearLayoutCompat layout = new LinearLayoutCompat(this);
LinearLayoutCompat.LayoutParams params = new LinearLayoutCompat.LayoutParams(LinearLayoutCompat.LayoutParams.MATCH_PARENT, LinearLayoutCompat.LayoutParams.MATCH_PARENT);
layout.setLayoutParams(params);
layout.setGravity(Gravity.CENTER);
layout.setOrientation(LinearLayoutCompat.VERTICAL);
mCursor.moveToFirst(); //Each iteration adds one TextView
do {
AppCompatTextView defaultText = new AppCompatTextView(this);
defaultText.setText(mCursor.getString(mCursor.getColumnIndex(DataBaseHelper.COLUMN_TYPES)));
defaultText.setTextAppearance(getApplicationContext(), R.style.TextFontMain);
defaultText.setTextSize(30);
defaultText.setPadding(0,30,0,30);
final String temp = (String) defaultText.getText();
defaultText.setGravity(Gravity.CENTER);
defaultText.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
Toast.makeText(getApplicationContext(), temp, Toast.LENGTH_SHORT).show();
}
});
layout.addView(defaultText);
mCursor.moveToNext();
} while(mCursor.isAfterLast() == false);
return layout; //LinearLayoutCompat containing all Texts returned
}
@Override
protected void onResume() {
super.onResume();
}
@Override
protected void onPause() {
super.onPause();
vegDBSource.close();
overridePendingTransition(android.R.anim.slide_in_left, android.R.anim.slide_out_right);
}
}
我先前的问题已被低估，但这次我做了大量的研究并找到了正确的方法，但我不能在我的独特案例中使用它
栈跟踪
6-05 19:32:17.679 3450-3450/com.techpappy.whattoeat E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.techpappy.whattoeat, PID: 3450
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.techpappy.whattoeat/com.techpappy.whattoeat.VegOptions}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.content.Context.getApplicationContext()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2567)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.content.Context.getApplicationContext()' on a null object reference
at android.content.ContextWrapper.getApplicationContext(ContextWrapper.java:106)
at com.techpappy.whattoeat.VegOptions.<init>(VegOptions.java:33)
at java.lang.Class.newInstance(Native Method)
at android.app.Instrumentation.newActivity(Instrumentation.java:1078)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2557)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
答案 0 :(得分：0)
只需在onCreate（）方法中初始化LayoutInflator，View和ViewGroup，问题就解决了。