我目前正在经历的应用程序的 Android 开发(使用 Android Studio)的第二个问题。详细说明:
目标:两个箭头，一个向上，一个向下。上方和下方的框包含每次都不同的信息。
问题:在这里，我尝试根据我首先设置为 0 的变量来设置条件。如果按下向上箭头并且该变量为 0，则不执行任何操作，否则递减该变量数字。同样，如果按下向下箭头且变量为 9，则不执行任何操作，否则增加该数字。
所以这就是发生的事情。我的代码:
package com.example.savag.myapplication;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.media.Image;
import android.provider.Settings;
import android.support.v4.content.res.ResourcesCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.hardware.Sensor;
import android.hardware.SensorManager;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity implements SensorEventListener{
//Define the sensor Manager
SensorManager sm;
//Define the Motion Sensor objects
Sensor accelerometer;
Sensor gravity;
Sensor gyroscope;
//Sensor uncalgyro;
Sensor lineaccel;
Sensor rotatevector;
//Sensor sigmotion;
//Sensor stepcounter;
//Sensor stepdetector;
//Define the changing Motion Sensor text values
TextView gyrosense;
//TextView uncalgyrosense;
TextView acceleration;
TextView gravitysense;
TextView lineaccelsense;
TextView rotatesense;
//TextView sigmotionsense; //In order to make use of this, use onTrigger event
//TextView stepstaken;
//TextView stepdetected; //In order to make use of this, use onTrigger event
//Define the position sensor objects
Sensor gamerotatevector;
//Define the changing Position sensor objects
TextView gamerotatesense;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//variable declare
final ImageButton button1 = (ImageButton)findViewById(R.id.motbut_unpressed);
final ImageView topbar2 = (ImageView)findViewById(R.id.topbarmain);
final ImageButton button2 = (ImageButton)findViewById(R.id.posbut_unpressed);
final ImageButton button3 = (ImageButton)findViewById(R.id.envbut_unpressed);
final LinearLayout andfield = (LinearLayout)findViewById(R.id.babcocklayout);
final ImageButton arrowup = (ImageButton)findViewById(R.id.uparrow);
final ImageButton arrowdown = (ImageButton)findViewById(R.id.downarrow);
final ImageView navbar = (ImageView)findViewById(R.id.infospace);
int counter;
counter = 0;
final String strcounter;
strcounter = Integer.toString(counter);
//Set Nav bar invisible for now
arrowup.setVisibility(View.GONE);
arrowdown.setVisibility(View.GONE);
navbar.setVisibility(View.GONE);
button1.setOnClickListener( //This is for the motion button
new ImageButton.OnClickListener() {
public void onClick(View v) {
button1.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.motionbutton_pressed, null));
topbar2.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.topbarmotion, null));
ndfield.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.logoandbarmotion, null));
//make sure the other two buttons are normal again
button2.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.positionbutton_normal, null));
button3.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.envirobutton_normal, null));
//make the arrows and infospace appear
arrowup.setVisibility(View.VISIBLE);
arrowdown.setVisibility(View.VISIBLE);
navbar.setVisibility(View.VISIBLE);
}
}
);
button2.setOnClickListener( //This is for the position button
new ImageButton.OnClickListener(){
public void onClick(View v){
button2.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.positionbutton_pressed, null));
topbar2.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.topbarposition, null));
andfield.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.logoandbaralternate, null));
//make sure the other two buttons are normal again
button1.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.motionbutton_normal, null));
button3.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.envirobutton_normal, null));
arrowup.setVisibility(View.VISIBLE);
arrowdown.setVisibility(View.VISIBLE);
navbar.setVisibility(View.VISIBLE);
}
}
);
button3.setOnClickListener( //This is for the environment button
new ImageButton.OnClickListener(){
public void onClick(View v){
button3.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.envirobutton_pressed, null));
topbar2.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.topbarenviro, null));
andfield.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.logoandbaralternate, null));
//make sure the other two buttons are normal again
button1.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.motionbutton_normal, null));
button2.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.positionbutton_normal, null));
arrowup.setVisibility(View.VISIBLE);
arrowdown.setVisibility(View.VISIBLE);
navbar.setVisibility(View.VISIBLE);
}
}
);
arrowup.setOnClickListener( //This is for the environment button
new ImageButton.OnClickListener(){
public void onClick(View v){
if (strcounter.equals("0"))
{
}
else
{
counter--; //how many times
strcounter = Integer.toString(counter);
//et1.setText(strcounter);
//now lets set text accordingly
if (strcounter.equals("1")) {
}
}
}
});
}
@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 void onAccuracyChanged(Sensor sensor, int accuracy) {
}
@Override
public void onSensorChanged(SensorEvent event) {
}
@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);
}
}
所以我们运行这个，我们得到这个错误:“局部变量计数器在内部类中访问；需要被声明为最终的”但是我不想要这个，因为这本质上是我 promise 我不会做任何事情这个变量。这是一个谎言，我想对这个变量做一切事情。而且 final int 也不起作用。
我无法解决这个该死的问题。好吧，那么我想，全局变量。不，也不起作用。
有人可以解释一下吗？非常感谢。
最佳答案
如错误消息所示，counter 是 onCreate() 方法内的局部变量。一旦 onCreate() 结束，它就会消失。这就是为什么你不能从内部类引用它。
将其移至类的一个字段(也称为数据成员、成员变量)，与所有其他字段一起:
public class MainActivity extends AppCompatActivity implements SensorEventListener{
int counter=0;
//Define the sensor Manager
SensorManager sm;
//Define the Motion Sensor objects
Sensor accelerometer;
Sensor gravity;
// and so on
关于java - Android开发-内部类中的变量，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/32854440/