Arraylist populating Listview in separate class not working

问题

I'm trying to add an item to arraylist/adapter on a Button click in my class

MyMaxes.java:

Date currentDate = new Date();
ArrayAdapter<Record> records = new ArrayAdapter<Record>(getApplicationContext(), R.layout.custom_record);
records.add(new Record(currentDate ,maxSquat, maxBench, maxDead, maxTotal));
records.notifyDataSetChanged();

And in my other class, MyProgress.java, I'm trying to assign that adapter to the ListView:

ListView listViewRec = (ListView) findViewById(R.id.listViewRecord);
listViewRec.setAdapter(records);

The records is underlined and says "Expression Expected".
I feel I need to set the TextViews in my custom layout file in the adapter somehow so it knows which item to put in which TextView.
Am I supposed to have an adapter class?

here is my custom_record:

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

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Date"
        android:textSize="18sp"
        android:id="@+id/txtDate"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Bench"
        android:id="@+id/txtBench"
        android:paddingRight="5dp"
        android:textSize="18sp"
        android:layout_gravity="center_horizontal"
        android:layout_alignParentTop="true"
        android:paddingLeft="5dp"
        android:layout_toLeftOf="@+id/txtSquat"
        android:layout_toStartOf="@+id/txtSquat"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Squat"
        android:textSize="18sp"
        android:paddingRight="5dp"
        android:id="@+id/txtSquat"
        android:layout_alignParentTop="true"
        android:paddingLeft="5dp"
        android:layout_toLeftOf="@+id/txtDead"
        android:layout_toStartOf="@+id/txtDead"
        />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Dead"
        android:paddingRight="5dp"
        android:textSize="18sp"
        android:id="@+id/txtDead"
        android:layout_alignParentTop="true"
        android:paddingLeft="5dp"
        android:layout_toLeftOf="@+id/txtTotal"
        android:layout_toStartOf="@+id/txtTotal"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Total"
        android:textSize="18sp"
        android:paddingRight="5dp"
        android:paddingLeft="5dp"
        android:id="@+id/txtTotal"
        android:layout_marginRight="34dp"
        android:layout_marginEnd="34dp"

        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"/>
</RelativeLayout>

and my custom object:

public class Record {

    private Integer squat, bench, dead;
    private double total;
    private Date dateTime;

    public Record(Date date,int squat, int bench, int dead, double total) {
        this.bench = bench;
        this.dateTime = date;
        this.dead = dead;
        this.squat = squat;
        this.total = total;
    }

    public Integer getSquat() {
        return squat;
    }

    public void setSquat(Integer squat) {
        this.squat = squat;
    }

    public Integer getBench() {
        return bench;
    }

    public void setBench(Integer bench) {
        this.bench = bench;
    }

    public Integer getDead() {
        return dead;
    }

    public void setDead(Integer dead) {
        this.dead = dead;
    }

    public Double getTotal() {
        return total;
    }

    public void setTotal(Integer total) {
        this.total = total;
    }

    public Date getDateTime() {
        return dateTime;
    }

    public void setDateTime(Date dateTime) {
        this.dateTime = dateTime;
    }
}

Edit ::Verify example::

main activity code:

public class MainActivity extends AppCompatActivity {

    Button mButton;
    Integer maxSquat = 1;
    Integer maxBench = 1;
    Integer maxDead = 1;
    Double maxTotal = 3.0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mButton= (Button) findViewById(R.id.btnTest);
        mButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Date currentDate = new Date();
                ArrayAdapter<Record> records = new ArrayAdapter<Record>(getApplicationContext(), R.layout.custom_record);
                records.add(new Record(currentDate ,maxSquat, maxBench, maxDead, maxTotal));
                records.notifyDataSetChanged();
            }
        });
    }
}

listview.java:

public class listview extends MainActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.listview);

        ListView listViewRec = (ListView) findViewById(R.id.listViewRecord);
        listViewRec.setAdapter(records);
    }
}

listview.xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:orientation="vertical"
          android:layout_width="match_parent"
          android:layout_height="match_parent">

<ListView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/listViewRecord"/>

activitymain.xml:

<RelativeLayout
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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.bestworkouts.myapplication.MainActivity">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hello World!"/>

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/btnTest"/>

I then have the record.java class from above, as well as the custom_record.xml from above.
Oddly enough, this one gives me a different error, it cannot resolve "records" when setting the adapter, where in my app it says "Expression Expected" for records.

回答1:

Why can't you have one view with a Button and a ListView that you add to?

Your first problem - you can't reference the local variable records from anywhere outside the click listener. This is a compilation error.

Second problem - you would be creating a brand new, empty adapter each time you clicked the button, then only adding one Record to it.

activitymain.xml

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/listViewRecord"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/btnTest"/>

</LinearLayout>

Let's call this RecordActivity because it displays and adds records to a ListView.

I would suggest using an AlertDialog to show a popup View when you click the button to get a Record object.

public class RecordActivity extends AppCompatActivity {

    Button mButton;
    ArrayAdapter<Record> mAdapter;
    ListView listViewRec;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mButton= (Button) findViewById(R.id.btnTest);
        mAdapter = new ArrayAdapter<Record>(getApplicationContext(), R.layout.custom_record);
        listViewRec = (ListView) findViewById(R.id.listViewRecord);
        listViewRec.setAdapter(mAdapter);

        mButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mAdapter.add(getRecord());
            }
        });
    }

    private Record getRecord() {
        Date currentDate = new Date();
        // TODO: Get your max values from somewhere
        int maxSquat = 1;  // TODO: From input field
        int maxBench = 1; // TODO: From input field
        int maxDead = 1; // TODO: From input field

        return new Record(currentDate ,maxSquat, maxBench, maxDead);
    }
}

Remove maxTotal from the parameters. You can calculate that inside the constructor of a Record.

public Record(Date date,int squat, int bench, int dead) {
    this.bench = bench;
    this.dateTime = date;
    this.dead = dead;
    this.squat = squat;
    this.total = bench + dead + squat;
}

来源：https://stackoverflow.com/questions/38907185/arraylist-populating-listview-in-separate-class-not-working

标签

android

listview

arraylist

android-arrayadapter